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SanDisk, Seagate, and Western Digital are not interchangeable storage stocks: SanDisk is primarily a NAND-flash business, while Seagate and the post-separation Western Digital are focused on mass-capacity hard disk drives (HDDs). A useful comparison therefore starts with product exposure and fiscal-period alignment, then tests whether revenue growth comes from price, shipped capacity, mix, or durable customer commitments. The latest filings show very different financial profiles, but they do not provide synchronized share prices or valuation multiples, so they cannot establish which stock is cheaper or the best buy.
This guide shows how to compare the three companies without mixing pre-spin Western Digital results with today’s standalone businesses, confusing GAAP earnings with recurring operations, or treating management guidance as achieved performance.
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At a glance
The order below follows business architecture, not an investment ranking. “Best for” describes the type of storage exposure each company provides.
| Name | Best for | Key spec | Checked |
|---|---|---|---|
| SanDisk (SNDK) | NAND/flash exposure, including data-center and edge storage | Q1 FY2027 revenue $11.031 billion; GAAP net income $8.101 billion | November 2026 |
| Seagate Technology (STX) | Mass-capacity HDD and data-center storage exposure | Q1 FY2027 revenue $4.233 billion; GAAP gross margin 57.3%; free cash flow $1.5 billion | November 2026 |
| Western Digital (WDC) | Standalone mass-capacity HDD exposure after the flash separation | Q4 FY2026 revenue $3.747 billion; GAAP operating income $1.563 billion | November 2026 |
Prices checked November 2026.
SanDisk’s quarter ended October 2, 2026, Seagate’s quarter ended October 2, 2026, and Western Digital’s fiscal fourth quarter ended July 3, 2026, are not the same reporting period. Keep those dates visible whenever you compare a number.
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What changed when SanDisk separated from Western Digital?
Western Digital distributed 80.1% of SanDisk to WD shareholders on February 21, 2025, and SanDisk began trading on Nasdaq on February 24, 2025. Western Digital’s remaining SanDisk shares were sold or exchanged by July 3, 2026. Western Digital now reports its HDD business, while SanDisk reports the flash business as a standalone company.
That break makes older WD totals a poor proxy for the current WD operation. In its continuing-operations presentation, WD says SanDisk results after the separation are no longer consolidated. A 2024 or early-2025 WD revenue or margin figure may include flash and HDD together, whereas a post-separation WD figure is predominantly HDD. Build a comparison using post-separation periods wherever possible and label any historical number that predates the split.
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How are the three storage businesses different?
SanDisk supplies NAND flash products, whose economics are shaped by bit growth, wafer supply, controller and technology transitions, and average selling prices (ASPs). Flash is used in data-center, edge, mobile, embedded, and consumer products. Seagate and Western Digital make HDDs, with demand concentrated in mass-capacity storage such as hyperscale and enterprise data centers. HDD and NAND can both benefit from expanding digital data, but they have different qualification cycles, manufacturing constraints, pricing behavior, and replacement patterns.
Seagate describes itself as a mass-capacity storage company. Its cited fiscal 2027 outlook is tied to data-center demand and its mass-capacity roadmap, rather than to NAND pricing. Western Digital’s post-spin results likewise represent an HDD-focused business. SanDisk’s filing, by contrast, says AI infrastructure growth is driving demand for high-performance storage and NAND. These are related secular themes, not identical end markets.
For an investor, the technology distinction is practical:
- SanDisk: ask whether NAND prices, exabytes shipped, product mix, and customer qualifications can support earnings when flash supply rises.
- Seagate: ask whether mass-capacity HDD demand, areal-density transitions, and data-center deployments support sustained volume and pricing.
- Western Digital: ask similar HDD questions, while also examining its own execution, product transition, balance sheet, and capital-allocation choices independently of Seagate.
Which fiscal periods can be compared directly?
Compare quarter with quarter and fiscal year with fiscal year, but do not assume that fiscal calendars line up. The available data provides SanDisk and Seagate quarters ended October 2, 2026, while WD’s fiscal Q4 and fiscal year ended July 3, 2026.
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| Company | Period in the latest figures | What it represents | Primary source |
|---|---|---|---|
| SanDisk | Q1 FY2027, three months ended October 2, 2026 | Standalone flash business | Form 10-Q |
| SanDisk | FY2026 ended July 3, 2026 | First full fiscal year presented as a standalone company in the cited results | Q4/FY2026 results |
| Seagate | Q1 FY2027, quarter ended October 2, 2026 | Mass-capacity HDD business | Q1 FY2027 results |
| Western Digital | Q4 FY2026 and FY2026 ended July 3, 2026 | Post-separation HDD continuing operations, plus a separate investment gain | Q4/FY2026 results |
When a company reports a non-GAAP measure, record the exact definition and reconciliation rather than placing it beside a GAAP number as if the measures were identical. The figures below are explicitly labeled GAAP unless noted otherwise.
What drove SanDisk’s recent revenue growth?
SanDisk reported $11.031 billion of revenue in fiscal Q1 2027, with $4.802 billion from Datacenter, $5.832 billion from Edge, and $397 million from Consumer. Total revenue rose 378% year over year; Datacenter increased 1,685%, Edge increased 320%, and Consumer declined 39%, according to the company’s October 2, 2026 Form 10-Q. Management attributed the Datacenter increase to higher sales and pricing, while Edge growth was primarily due to higher pricing.
The filing also says total products sold rose almost 10% on an exabyte basis. That distinction matters: revenue can grow because the company ships more bits, charges more for each bit, sells a richer mix, or combines all three. A 378% increase from a changed comparison base and a sharp market recovery should not be extrapolated mechanically.
SanDisk’s fiscal Q4 2026 release reported $8.965 billion of revenue, an 84.6% GAAP gross margin, and $6.903 billion of GAAP net income. For FY2026, revenue was $20.248 billion, up 175% year over year, with a 71.5% GAAP gross margin and $11.433 billion of GAAP net income. Sequential Q4 revenue growth was approximately one-third volume and two-thirds pricing. The large pricing contribution is a central durability question: investors should track whether future growth is supported by exabytes and customer expansion as well as ASPs.
SanDisk also describes New Business Model agreements that generally cover stated volumes over multiple years and use fixed and variable pricing mechanisms. The company says these arrangements are intended to improve revenue predictability and production planning. That is management’s stated rationale, not a promise that customers will take every volume or that margins will remain at a particular level.
How do Seagate and Western Digital’s HDD results compare with SanDisk’s flash results?
Seagate reported fiscal Q1 2027 revenue of $4.233 billion, a 57.3% GAAP gross margin, $1.761 billion of GAAP net income, and $1.5 billion of free cash flow. Western Digital reported fiscal Q4 2026 revenue of $3.747 billion, a 54.1% GAAP gross margin, and $1.563 billion of GAAP operating income. These margins are not an apples-to-apples ranking: SanDisk’s 84.6% quarterly gross margin reflects a flash pricing and mix environment, while Seagate and WD’s figures reflect HDD economics and different fiscal dates.
| Company and period | Revenue | GAAP profitability disclosed | Cash metric disclosed |
|---|---|---|---|
| SanDisk Q1 FY2027 (three months ended October 2, 2026) | $11.031 billion | Net income $8.101 billion | Operating cash flow $6.363 billion |
| SanDisk Q4 FY2026 | $8.965 billion | Gross margin 84.6%; net income $6.903 billion | Not included in the cited Q4 summary |
| SanDisk FY2026 | $20.248 billion | Gross margin 71.5%; net income $11.433 billion | Not included in the cited FY summary |
| Seagate Q1 FY2027 (quarter ended October 2, 2026) | $4.233 billion | Gross margin 57.3%; net income $1.761 billion | Free cash flow $1.5 billion |
| Western Digital Q4 FY2026 | $3.747 billion | Gross margin 54.1%; operating income $1.563 billion | Free cash flow $1.28 billion |
| Western Digital FY2026 continuing operations | $12.919 billion | Includes a separate $6.498 billion gain on retained SanDisk interest | Use operating cash flow and free cash flow disclosures separately from the gain |
Do not rank these percentages without first asking what is included in cost of sales, whether the period is a quarter or a year, and whether the business mix changed. Operating income is usually more informative than net income when a company has a major investment or separation item.
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What do cash flow, capital spending, and leverage reveal?
Cash conversion can distinguish a temporary accounting windfall from an operating improvement. SanDisk generated $6.363 billion of operating cash flow in Q1 FY2027 against $11.031 billion of revenue. That is an unusually strong quarter, so examine working-capital movements, inventory, receivables, and planned capital investment before treating the ratio as a steady-state margin.
SanDisk says FY2027 capital investments are expected to increase. Higher investment may be necessary to support data-center and edge demand, but it also raises execution and funding requirements. Compare capital expenditure with operating cash flow and free cash flow over several periods; a company can report high net income while cash is absorbed by capacity, inventory, or receivables.
Seagate reported $1.5 billion of Q1 FY2027 free cash flow. Gross debt was $2.4 billion at quarter end, and the company said it retired another $750 million of principal after quarter end, bringing gross debt to $1.6 billion. The post-quarter debt figure is a subsequent event, not part of the quarter-end balance sheet. Track debt repayment alongside dividends, buybacks, maintenance capital expenditure, and the cash needed for HDD technology transitions.
Western Digital reported Q4 FY2026 free cash flow of $1.28 billion. Keep that cash figure separate from the $6.498 billion gain on the retained SanDisk interest: the gain increases reported earnings but does not represent cash generated by selling HDDs in the quarter. Review the company’s Form 10-K for cash-flow classification and continuing-operations details.
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Customer concentration can make a fast-growing storage company more vulnerable to a single design win, qualification delay, order change, or pricing negotiation. SanDisk’s Q1 FY2027 filing says two customers each accounted for 12% of quarterly revenue. That means the loss or postponement of one large account could affect reported revenue and factory planning disproportionately, even if industry demand remains healthy.
Concentration is not automatically negative. Multi-year commitments can improve production planning, and a large data-center customer can support rapid scale. The question is whether commitments are firm, how pricing is set, what penalties or take-or-pay features exist, and how much capacity is dedicated to that customer. Read contract descriptions together with revenue concentration rather than treating either item as a guarantee.
For Seagate and Western Digital, review customer and channel disclosures in each filing, along with data-center concentration and inventory at distributors. HDD demand can be lumpy because a small number of hyperscale customers can place large orders tied to build-out schedules. Compare backlog or demand-visibility statements with actual shipments and cash collection in later quarters.
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What risks could reverse the current earnings picture?
The three companies share exposure to the storage cycle, but the mechanisms differ.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match- Pricing cycles: NAND ASPs can fall quickly when supply exceeds demand. HDD pricing and mix can also weaken when customers defer capacity purchases.
- Technology transitions: SanDisk faces NAND-node, layer-count, controller, and qualification transitions; HDD makers face areal-density and product-roadmap execution. Delays can raise costs or postpone revenue.
- Supply and manufacturing: A disruption at a fabrication, component, or assembly partner can reduce shipments and leave fixed costs under-absorbed.
- Customer dependence: SanDisk’s two 12% customers illustrate the effect of concentration. Large HDD customers can create similar order volatility.
- Capital intensity: SanDisk expects higher FY2027 investment. Capacity that arrives late, costs more than planned, or is not matched by demand can pressure free cash flow.
- Macro and industry cycles: Enterprise and cloud spending can be delayed by budgets, while consumer electronics demand can weaken independently of data-center demand.
- Balance-sheet risk: Debt maturities, buybacks, dividends, and capital spending compete for cash during a downturn.
SanDisk’s filing specifically identifies volatile demand and ASPs, competition, technology transitions, manufacturing and supply disruptions, reliance on strategic partners, customer relationships, and industry cycles. Seagate’s release also warns that forward-looking outcomes can differ from management expectations. Treat every outlook statement as a scenario, not a result.
How should I treat Seagate’s fiscal Q2 2027 guidance?
Seagate guided to fiscal Q2 2027 revenue of $4.8 billion, plus or minus $100 million. That is management guidance, not reported performance. The range implies a $4.7 billion to $4.9 billion revenue interval, but it says nothing by itself about gross margin, free cash flow, product mix, or the timing of customer purchases.
When the quarter is reported, compare actual revenue with the midpoint and range, then explain the variance using shipped capacity, pricing, mix, and customer timing. Also check whether debt repayment and capital allocation matched the assumptions embedded in management’s outlook. Do not use guidance to backfill a missing valuation or to claim that Seagate will outperform either flash or HDD peers.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How do I build a fair SanDisk, Seagate, and Western Digital stock comparison?
Use a worksheet that keeps periods, definitions, and business drivers visible. The following sequence avoids the most common errors.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errors- Freeze the reporting date. Write the fiscal end date beside every number. Use the October 2, 2026 quarters for SanDisk and Seagate together, and label WD’s July 3, 2026 year and quarter separately.
- Separate the businesses. Mark SanDisk as NAND/flash and Seagate and WD as HDD. Remove pre-spin WD figures from a direct standalone comparison unless you explicitly adjust for the former flash segment.
- Record revenue by driver. For SanDisk, split Datacenter, Edge, and Consumer and note the exabyte, pricing, and mix disclosures. For HDD companies, capture shipped capacity, data-center demand, product transitions, and any disclosed customer commitments.
- Use like-for-like profitability. Put GAAP gross margin beside GAAP gross or operating income for the same period. Add non-GAAP figures only after recording the company’s reconciliation and exclusions.
- Bridge earnings to cash. Capture operating cash flow, free cash flow, capital expenditure, inventory, and receivables. Flag one-off gains, especially WD’s $6.498 billion retained-SanDisk-interest gain.
- Assess the balance sheet. Record gross debt, cash, maturities, repayments, dividends, and buybacks. Seagate’s post-quarter reduction from $2.4 billion to $1.6 billion gross debt should be labeled as subsequent to quarter end.
- Score concentration and execution. Note SanDisk’s two customers at 12% each, the status of multiyear agreements, qualification timing, supply dependencies, and capacity plans.
- Write an explicit uncertainty paragraph. State which assumptions depend on pricing, volume, customer commitments, or management guidance. A comparison is more useful when it shows what would falsify the thesis.
What should a valuation comparison include?
A relative-valuation conclusion requires a synchronized market snapshot that is not supplied here. Collect the same-date share price, diluted share count, market capitalization, net debt, and enterprise value for all three companies. Then calculate consistently defined measures such as price-to-earnings, enterprise-value-to-sales, and enterprise-value-to-operating-income or EBITDA, while documenting whether earnings are GAAP, adjusted, or affected by one-off items.
Use continuing operations for WD and exclude the $6.498 billion Sandisk-interest gain from any measure intended to represent recurring HDD earnings. For SanDisk, consider whether a price-led margin spike is sustainable before applying a full-cycle earnings multiple. For Seagate and WD, distinguish a cyclical recovery year from normalized HDD profitability. The available filings do not verify synchronized prices, market capitalizations, analyst estimates, or valuation multiples, so they cannot support a claim that one stock is currently cheaper, fairly valued, or the best buy.
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How we picked the comparison framework
The framework prioritizes the factors the companies’ filings make decision-relevant: product and technology exposure, end-market and customer mix, price versus volume, GAAP profitability, operating and free cash flow, capital requirements, leverage, accounting adjustments, and forward-looking risks. It uses company-reported figures and management guidance with explicit dates, and it treats the SanDisk separation as a hard break in the historical series. The framework is designed to help a reader reach an individual conclusion, not to rank the stocks without a common-time valuation dataset.
Bottom line: what can you conclude from the current filings?
SanDisk offers the clearest flash and NAND pricing exposure, with extraordinary FY2026 and Q1 FY2027 reported growth but substantial sensitivity to ASPs, mix, customer concentration, and higher planned investment. Seagate and Western Digital provide HDD-focused exposure, with Seagate showing Q1 FY2027 free cash flow and active debt reduction, and WD showing strong Q4 operating income and free cash flow but a fiscal-year headline distorted by the $6.498 billion investment gain.
The right comparison is therefore conditional: decide which storage technology, demand driver, cash profile, and risk set you want, then align fiscal periods and normalize one-time accounting items. A current stock-price or valuation verdict requires additional synchronized market data beyond these filings.
Frequently Asked Questions
Why can SanDisk’s gross margin be much higher than the HDD companies’ margins?
Flash and HDD have different cost structures, product mixes, and pricing cycles. SanDisk’s reported 84.6% Q4 FY2026 gross margin reflects a particular pricing and mix environment; it should not be treated as a structural margin floor or compared as a simple score against an HDD quarter.
What does SanDisk’s two-customer concentration mean for an investor?
Two customers each represented 12% of Q1 FY2027 revenue, so a delay or reduction from one account could move quarterly results materially. Check whether volume commitments, pricing mechanisms, and capacity plans would cushion that effect rather than assuming concentration automatically predicts a loss.
How should I compare free cash flow between the companies?
Use the same period and definition, then inspect capital expenditure and working-capital movements. A quarter with unusually favorable receivables or inventory timing can make free cash flow look stronger than a normalized year, while capacity investment can temporarily depress cash even when demand is healthy.
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Does Western Digital’s Sandisk-related gain increase the cash available to its HDD business?
The $6.498 billion gain is an accounting result tied to the retained Sandisk interest, not HDD operating revenue. Review the cash-flow statement and the company’s continuing-operations disclosures to determine what cash was actually received and how it was allocated.
What additional data is needed before choosing among these stocks?
You would need a same-date price and share-count snapshot, net debt, consistently defined valuation ratios, and a view of normalized earnings through a storage cycle. Updating customer commitments, capacity spending, and subsequent quarterly cash flow is also important because the cited guidance and results can change quickly.
