Excel has no standard built-in RSI() worksheet function, but you can calculate the conventional 14-period Relative Strength Index from closing prices with ordinary formulas. The method below builds a transparent, reusable worksheet using J. Welles Wilder’s smoothing method—the version most commonly intended by “standard RSI.”
You will calculate price changes, separate gains from losses, seed the first average gain and loss, apply Wilder smoothing, and produce RSI values that can be copied down as new prices arrive.
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What RSI measures
The Relative Strength Index is a bounded momentum oscillator from 0 to 100. It compares the magnitude of recent upward closing-price movements with recent downward movements:
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RSI = 100 - (100 / (1 + RS))
where:
RS = Average Gain / Average Loss
Wilder’s conventional default is 14 periods. RSI measures recent price momentum—not a stock’s absolute price, intrinsic value, or guaranteed future direction. Readings above 70 are commonly called overbought and readings below 30 oversold, but RSI can remain above 70 in a strong uptrend or below 30 in a strong downtrend.
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The formulas and initialisation used here follow the Wilder-style calculation documented by StockCharts.
Prepare the Excel worksheet
Use a clean chronological series with the oldest observation first. A practical worksheet can use these columns:
| Column | Header | Purpose |
|---|---|---|
| A | Date | Trading date or bar timestamp |
| B | Close | Closing price for each period |
| C | Change | Current close minus previous close |
| D | Gain | Positive price change only |
| E | Loss | Negative price change expressed as a positive magnitude |
| F | Average Gain | Initial average, then Wilder-smoothed gain |
| G | Average Loss | Initial average, then Wilder-smoothed loss |
| H | RS | Average gain divided by average loss |
| I | RSI | Final 0–100 indicator |
Put the lookback period in K1 and enter 14 there. You can also use K2 for an overbought reference level of 70 and K3 for an oversold reference level of 30.
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Data requirements
- Use at least 15 closing prices for a 14-period RSI: 14 changes require 15 prices.
- Sort dates from oldest to newest.
- Use one consistent timeframe and one observation per intended period.
- Check for missing values, duplicate timestamps, and nonnumeric prices.
- Use a consistent adjusted or unadjusted price series when comparing with another platform.
More history is preferable because the first average is a seed for a recursive series. Different starting dates can produce slightly different early RSI values.
Step 1: Calculate each price change
Put the first date in row 2 and its closing price in B2. Leave C2 blank because there is no earlier close for comparison.
In C3, enter:
=B3-B2Copy the formula down. A positive result is an upward move, a negative result is a downward move, and zero means the price did not change.
Step 2: Separate gains and losses
In D3, enter:
=MAX(C3,0)In E3, enter:
=MAX(-C3,0)Copy both formulas down.
This creates two nonnegative series:
- A positive change produces a gain and zero loss.
- A negative change produces zero gain and a positive loss.
- An unchanged price produces zero for both.
Do not average signed negative changes in the loss column. The average loss must represent the magnitude of downward movement.
Step 3: Calculate the first 14-period averages
With the layout above, the first 14 changes occupy rows 3 through 16. Therefore, the first 14-period RSI appears on row 16—not row 14—because the calculation needs 15 closing prices.
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In F16, enter:
=AVERAGE(D3:D16)In G16, enter:
=AVERAGE(E3:E16)These are the seed averages. They are simple averages of the first 14 gains and the first 14 loss magnitudes.
For a reusable variable-period sheet, the initial range must contain exactly the first K1 valid changes. The fixed ranges above are easiest to audit for a 14-period worksheet.
Step 4: Apply Wilder’s smoothing
For each later row, Wilder’s method updates the previous average rather than recalculating a simple moving average over only the most recent 14 rows.
In F17, enter:
=((F16*($K$1-1))+D17)/$K$1In G17, enter:
=((G16*($K$1-1))+E17)/$K$1Copy both formulas down. With K1 set to 14, these are equivalent to:
=((F16*13)+D17)/14=((G16*13)+E17)/14The previous average receives a weight of 13 out of 14, while the current gain or loss receives a weight of 1 out of 14. This is Wilder smoothing, not an ordinary rolling AVERAGE().
Step 5: Calculate relative strength and RSI
In H16, enter:
=IF(G16=0,"",F16/G16)Copy it down if you want to display RS. The blank result avoids a division-by-zero error when average loss is zero.
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=IF(G16=0,IF(F16=0,50,100),100-(100/(1+F16/G16)))Copy the formula down.
This handles the important edge cases:
- If average loss is zero and average gain is positive, RSI returns 100.
- If average gain and average loss are both zero, this worksheet returns 50 because there was no directional movement.
- If average loss is positive, Excel calculates the standard RSI expression.
The all-zero convention is not universal. Some software may return a blank or use another treatment, so disclose it when comparing results.
A small example layout
For a quick test, enter these fictional closing prices in chronological order in B2:B19:
100, 101, 100, 100, 102, 101, 103, 102, 104, 105, 104, 106, 105, 107, 106, 108, 109, 108This sample includes positive, negative, and flat changes. The first RSI is produced in row 16. Rows 17 and 18 then demonstrate the recursively smoothed averages and subsequent RSI values. Keep full precision in the formulas and format column I to display two decimal places; do not round the intermediate gains, losses, or averages.
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Keep incomplete rows blank
If your sheet may contain fewer than the required number of prices, do not display a partial-period RSI. A basic guard for the first output row can be written as:
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=IF(COUNT($B$2:B2)<$K$1+1,"",your_RSI_formula)For a production worksheet, it is usually clearer to leave the initial calculation rows blank and begin the seed formulas only after the required number of valid changes exists. Missing or text values should be cleaned rather than silently treated as zero.
Fill formulas down safely
- Confirm that the first RSI row uses the seed averages.
- Confirm that the next row refers to the prior average, such as
F16in row 17. - Confirm that
$K$1remains fixed in every copied formula. - Use Excel’s fill handle to copy formulas down as new closing prices are added.
- Format the RSI column as a number with two decimal places if desired.
For a live or regularly updated workbook, append new rows below the existing data and copy the formulas into those rows. A clean Excel Table can make formula propagation easier, but the underlying calculation remains the same.
Add an RSI chart
- Select the Date column and the RSI column.
- Choose Insert and add a line chart. Menu wording can vary between Excel desktop, Excel for the web, and Mac.
- Set the vertical axis from 0 to 100 if that improves readability.
- Add horizontal reference series at 70 and 30 if you want overbought and oversold guides.
One simple approach is to create two helper columns containing the constant values 70 and 30 for each date, then add those columns to the chart. Label the chart as an RSI momentum indicator, not as an automatic buy-or-sell system.
Troubleshoot RSI mismatches
If your result differs from a charting platform or another calculator, compare the intermediate columns rather than only the final RSI.
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A 14-period RSI needs 14 valid changes and therefore 15 closing prices. Starting the first average too early shifts the entire series.
Signed losses
Column E must contain positive loss magnitudes. =MIN(C3,0) produces negative values and is not the loss series used by the formula above.
Rolling averages instead of Wilder smoothing
Using AVERAGE() for every later row calculates a simple-moving-average version, often associated with Cutler’s RSI, not Wilder’s conventional recursive RSI.
Different historical starting points
Because later values depend on earlier averages, two calculations can differ when one begins with more historical data. Use a longer identical history when comparing platforms.
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Different price data
Check whether both sources use adjusted or unadjusted prices, the same session close, the same timeframe, and the same missing-bar policy. A split or dividend adjustment can create a large change if the series is inconsistent.
Rounding
Do not round intermediate values. Round only the displayed RSI. Early rounding can create small but persistent differences.
Manual calculation mode
If formulas do not update, open the Formulas tab, choose Calculation Options, and select Automatic. Excel can also recalculate manually when calculation mode is set to Manual. Microsoft documents these settings at Change formula recalculation, iteration, or precision in Excel.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Wilder RSI versus Cutler’s RSI
Not every indicator labelled “RSI” uses the same calculation.
| Method | Average calculation | Typical effect |
|---|---|---|
| Wilder RSI | Initial simple average, followed by recursive Wilder smoothing | Smoother and commonly associated with the conventional default |
| Cutler’s RSI | Simple moving averages of gains and losses | Can change more abruptly as observations leave the lookback window |
| EMA-based variation | Exponential smoothing using a specified EMA convention | May use a different weighting constant and produce different values |
LSEG’s technical-analysis documentation discusses distinctions between Wilder smoothing, EMA-style calculations, and other RSI implementations. Identify the method before comparing results.
How to interpret RSI responsibly
- Above 70: recent upward momentum has been strong relative to recent declines; it does not guarantee a reversal.
- Below 30: recent downward momentum has been strong; it does not guarantee a rebound.
- Near 50: average gains and losses are more balanced, although the exact relationship depends on the formula and data.
- Divergence: a new price high or low that is not confirmed by RSI can be a reason to investigate momentum, not a standalone trade instruction.
- Failure swings: repeated RSI highs or lows can provide additional context when confirmed by price structure.
- Centerline crosses: movement above or below 50 can help describe momentum direction.
Thresholds can be interpreted in trend context. Some analysts watch approximately 40–80 ranges in strong uptrends and 20–60 ranges in strong downtrends instead of treating 30 and 70 as universal reversal boundaries. Confirmation from price structure, support and resistance, volume, or another independent measure is important. RSI alone is not a reliable prediction tool or investment recommendation.
Verification checklist
- The first RSI appears only after 14 valid price changes.
- Dates are sorted oldest to newest.
- Prices are numeric and the series has no unintended blanks or duplicate bars.
- Gains and losses are never negative.
- The first averages use the first 14 gains and 14 loss magnitudes.
- Later averages use the prior average and current gain or loss—not a new rolling average.
- RSI values remain between 0 and 100.
- Zero average loss is handled explicitly.
- Both average gain and average loss being zero follows a documented convention.
- Comparisons use the same period, timeframe, price field, adjustments, history, smoothing method, and rounding policy.
Excel versus a charting platform
Excel is a good choice when you want every intermediate calculation visible, auditable, and adaptable to a broader financial model. A charting platform is more convenient when you need instant indicators, alerts, multiple timeframes, or market data without building the worksheet. A data add-in is useful only when live or automated imports justify the added complexity; it is not required to calculate historical RSI in Excel.
The transparent column-by-column method is also preferable for learning and troubleshooting. Compact modern-Excel formulas using functions such as LET, SCAN, or LAMBDA can reduce visible columns, but they are version-dependent and make it harder to audit the seed and smoothing steps. The method above relies on longstanding functions such as MAX, AVERAGE, and IF, making it broadly suitable for modern Excel desktop and Excel for the web.
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