# Relative Strength Index Calculator (RSI)

URL: https://speedycalculator.com/calculators/finance/relative-strength-index/
Last updated: 2026-10-25

> The RSI calculator works out the relative strength index of a list of closing prices using Wilder's smoothing – for any period (14 by default) – and whether the asset looks overbought or oversold, along with simple, exponential and weighted moving averages.

## Inputs

- Closing prices (oldest first)
- RSI period
- Moving-average length

## Results

- Relative strength index (RSI)
- Signal
- Simple moving average
- Exponential moving average
- Weighted moving average
- SMA series (period: value)

## Formula

```
Average gain and loss over the first n periods, then smoothed: avg = (previous avg × (n − 1) + current) ÷ n
RS = average gain ÷ average loss
RSI = 100 − 100 ÷ (1 + RS)
```

## Explanation

J. Welles Wilder introduced the RSI in 1978. Readings above 70 are traditionally read as overbought and below 30 as oversold; in strong trends RSI can stay extreme for a long time. Everything is calculated in your browser, so nothing you type is sent to our server.

### How to use the Relative Strength Index Calculator

- **Closing prices (oldest first)**
- **RSI period**
- **Moving-average length**

Everything runs in your browser, so results appear instantly and nothing you type is sent to a server.

### How it works

Paste closing prices in date order (oldest first) and choose the RSI period and moving-average length.

### Tips

- Enter figures for the same period and in the same currency.
- Exchange rates and prices change constantly – update them before you rely on a result.
- Use results as estimates and confirm important figures with the official source.
- Everything runs in your browser – try different values to compare scenarios.

### Common mistakes to avoid

- Mixing gross and net figures.
- Using outdated rates.
- Treating rules of thumb as exact.

## Worked example

Inputs — Closing prices (oldest first): 44.34, 44.09, 44.15, 43.61, 44.33, 44.83, 45.10, 45.42, 45.84, 46.08, 45.89, 46.03, 45.61, 46.28, 46.28, 46.00, 46.03, 46.41, 46.22, 45.64; RSI period: 14; Moving-average length: 10.

Results — **Relative strength index (RSI) = 57.92**; Signal = Neutral; Simple moving average = 46.039; Exponential moving average = 45.8704; Weighted moving average = 46.0576; SMA series (period: value) = 10: 44.779
11: 44.934
12: 45.128
13: 45.274
14: 45.541
15: 45.736
16: 45.853
17: 45.946
18: 46.045
19: 46.083
20: 46.039.

## FAQ

**What is the RSI?**
A momentum oscillator from 0 to 100 measuring the speed of price changes.

**What RSI period should I use?**
14 is standard; shorter periods are more sensitive.

**What does RSI above 70 mean?**
The asset may be overbought.

**What formula does the Relative Strength Index Calculator use?**
Average gain and loss over the first n periods, then smoothed: avg = (previous avg × (n − 1) + current) ÷ n.