Forex Stochastic Oscillator
The Stochastic Oscillator shows where the current price closed compared with its recent high-low range. It moves between 0 and 100 and helps you spot when a move is stretched.
What is the Stochastic?
George Lane made the stochastic popular in the 1950s. His idea was simple:
- In an uptrend, prices tend to close near the top of their recent range.
- In a downtrend, prices tend to close near the bottom of their recent range.
The stochastic turns that into a number. A reading of 100 means price closed at the highest point of the lookback period. A reading of 0 means it closed at the lowest point.
Like RSI, it is an oscillator: an indicator that swings between fixed limits, shown in a panel under the price chart.
The Formula: %K and %D
The stochastic has two lines.
- Lowest Low and Highest High are taken over the lookback period, usually 14 candles.
- %K is the main, faster line.
- %D is a smoothed version of %K, used as a signal line.
Example — calculating %K
EUR/USD daily chart. Over the last 14 days the highest high is 1.0900 and the lowest low is 1.0800. Today closes at 1.0875.
%K = (1.0875 − 1.0800) ÷ (1.0900 − 1.0800) × 100 = 0.0075 ÷ 0.0100 × 100 = 75 pips ÷ 100 pips × 100 = 75
Price closed 75% of the way up its 14-day range.
Example — three days and %D
| Day | 14-day high | 14-day low | Close | %K |
|---|---|---|---|---|
| 1 | 1.0900 | 1.0800 | 1.0875 | 75 ÷ 100 = 75.0 |
| 2 | 1.0910 | 1.0800 | 1.0890 | 90 ÷ 110 = 81.8 |
| 3 | 1.0910 | 1.0800 | 1.0845 | 45 ÷ 110 = 40.9 |
%D (day 3) = (75.0 + 81.8 + 40.9) ÷ 3 = 197.7 ÷ 3 = 65.9
On day 3, %K (40.9) is below %D (65.9). %K has crossed down through %D — a bearish crossover.
Note: On day 2 the range grew because a new 14-day high was made. The stochastic always measures the close against the current range, so the denominator changes as old candles drop out.
Fast vs Slow Stochastic
The raw formula above is the fast stochastic. It is very jumpy. Most platforms show the slow stochastic by default, which smooths it once more.
| Version | %K line | %D line | Character |
|---|---|---|---|
| Fast (14, 3) | Raw %K | 3-SMA of raw %K | Quick, many signals, lots of noise |
| Slow (14, 3, 3) | 3-SMA of raw %K (= fast %D) | 3-SMA of slow %K | Smoother, fewer but cleaner signals |
| Full (14, 3, 3) | Custom smoothing | Custom smoothing | Lets you set every period |
On MetaTrader the default "Stochastic Oscillator" is 5, 3, 3. Many traders change it to 14, 3, 3. Shorter periods react faster; longer periods are smoother.
Tip: Pick one setting and stick with it while you learn. Switching settings until the indicator "fits" past trades is a form of curve fitting.
Overbought and Oversold: 80 and 20
- Above 80 — overbought: price is closing near the top of its range.
- Below 20 — oversold: price is closing near the bottom of its range.
- Between 20 and 80 — the neutral zone.
Warning: "Overbought" does not mean "about to fall". In a strong uptrend the stochastic can stay above 80 for days while price keeps rising. Selling every reading above 80 in a trend is one of the most common beginner mistakes.
Crossover Signals
The stochastic's main signal is a %K / %D crossover, especially in the extreme zones.
- Bullish — %K crosses above %D while both are below 20, then rises back above 20.
- Bearish — %K crosses below %D while both are above 80, then falls back below 80.
A crossover in the middle (around 50) is a weak signal. The best signals come from the extremes, at a price level that matters.
Example
USD/CAD falls to support at 1.3550. Slow stochastic reads %K = 12, %D = 15. The next candle closes higher: %K = 24, %D = 18.
%K crossed above %D in the oversold zone and moved back above 20, right at support. That is a bullish setup. Entry 1.3565, stop 1.3535 (30 pips) below support.
Using the Stochastic in Ranges
The stochastic works best when the market is moving sideways between clear support and resistance.
- Confirm a range: flat moving average, repeated touches of a top and bottom.
- Near the bottom, wait for a bullish crossover below 20.
- Near the top, wait for a bearish crossover above 80.
- Stop just outside the range. Target the other side or the middle.
Using the Stochastic in Trends
In a trend, flip your thinking. Use the stochastic to time pullbacks in the trend direction, and ignore signals against it.
| Market | Take | Ignore |
|---|---|---|
| Uptrend | Bullish crosses from below 20 (or 50) on pullbacks | Overbought "sell" readings |
| Downtrend | Bearish crosses from above 80 (or 50) on rallies | Oversold "buy" readings |
| Range | Both, at the range edges | Middle-of-range crosses |
Tip: Stochastic divergence works like RSI and MACD divergence: price makes a new high or low, the stochastic does not. See Divergence Trading.
Strengths and Weaknesses
Strengths
- Fast — reacts quicker than RSI.
- Fixed 0–100 scale, easy to read.
- Excellent for timing entries in ranges and pullbacks.
Weaknesses
- Very noisy on low timeframes.
- Stays overbought/oversold in strong trends.
- Needs a trend filter to avoid counter-trend losses.
Test Yourself With Exercises
The 14-period high is 1.2760, the low is 1.2680 and price closes at 1.2700. What is %K?
- 75
- 25
- 50
- 20
What is %D in the standard stochastic?
- A 3-period average of %K
- The 14-period high minus the low
- A 9-period EMA of price
Which levels usually mark overbought and oversold on the stochastic?
- 70 and 30
- 100 and 0
- 80 and 20
EUR/USD is in a strong uptrend and the stochastic is at 92. What is the most sensible view?
- Sell immediately — it is overbought
- The indicator is broken
- Strong trends can stay overbought; wait for a pullback to buy
Where does the stochastic work best on its own?
- During major news releases
- In strong trends
- On very low timeframes
- In sideways ranges