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Relative Strength Index Calculator

Calculate Relative Strength Index (RSI) for stock and crypto trading from price series or average gain and loss.

RSI (14 period)

70.46

Overbought (strong momentum, possible reversal)

RSI components

Relative strength (RS)
2.3857
Average gain
0.2386
Average loss
0.1000
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What is the Relative Strength Index (RSI)?

The Relative Strength Index (RSI) is a momentum oscillator developed by J. Welles Wilder Jr. that measures the speed and magnitude of recent price changes on a scale from 0 to 100. Traders use RSI to identify overbought conditions (typically above 70), oversold conditions (typically below 30), and shifts in bullish or bearish momentum.

This calculator supports two input modes: a comma-separated closing price series with Wilder smoothing, or direct average gain and average loss values. Pair RSI readings with pivot point levels for support and resistance context, and use the position size calculator to size trades around your risk tolerance.

RSI formula with Wilder smoothing

RS=Average GainAverage LossRS = \frac{\text{Average Gain}}{\text{Average Loss}}
RSI=100−1001+RSRSI = 100 - \frac{100}{1 + RS}

Wilder smoothing uses an exponential-style rolling average. The first average gain and average loss are simple means over the first N periods. Each subsequent value updates as:

Avg Gaint=Avg Gaint−1×(N−1)+GaintN\text{Avg Gain}_t = \frac{\text{Avg Gain}_{t-1} \times (N-1) + \text{Gain}_t}{N}

The same formula applies to average loss. When average loss equals zero and average gain is positive, RSI equals 100.

Worked example (14-period RSI)

Using the default 15 closing prices in this calculator with a 14-period setting, Wilder smoothing produces an RSI of approximately 70.46. That reading sits just above the traditional 70 overbought threshold, signaling strong upward momentum that may eventually cool.

How traders interpret RSI levels

  • Above 70: Often labeled overbought. Price may continue higher in strong trends, but reversal risk increases.
  • Below 30: Often labeled oversold. Downtrends can persist, but bounce potential rises.
  • 50 midpoint: Acts as a rough bull/bear dividing line in range-bound markets.

Frequently asked questions

What RSI period should I use?
The 14-period RSI is the industry default Wilder introduced. Shorter periods (7 or 9) react faster. Longer periods (21 or 25) smooth noise for swing trading.
Can RSI stay above 70 in a strong trend?
Yes. In powerful uptrends, RSI can remain overbought for extended periods. Treat 70 and 30 as reference zones, not automatic buy or sell triggers.
What is the difference between price series and average gain/loss modes?
Price series mode computes gains and losses from raw closes and applies Wilder smoothing automatically. Average gain/loss mode lets you plug in pre-smoothed values from a spreadsheet or charting platform.
How does RSI relate to other technical tools?
RSI measures momentum speed. Pivot points identify price levels. Position sizing converts account risk into share count. Use multiple tools together rather than relying on RSI alone.
Are my inputs stored on a server?
No. All RSI math runs in your browser. Changing fields updates the page URL so you can share a scenario without server storage.

Resources and references

The formulas and methods in this calculator were checked against these independent sources.