Stochastic Momentum Index (SMI) Explained: Formula, Settings, MT4/MT5

Last updated: August 31, 2026 · By: Tim Morris

The Stochastic Momentum Index (SMI) is a momentum oscillator built by William Blau in 1993 that measures where price closes relative to the midpoint of the recent high-low range, then double-smooths that reading. It swings roughly between -100 and +100, with zero marking the range midpoint, and reads cleaner than the classic stochastic.

What is the Stochastic Momentum Index?

The SMI answers one question: is price closing in the top half or the bottom half of its recent trading range, and by how much? A reading above zero means closes are sitting above the midpoint of the last N bars. A reading below zero means they are sitting below it.

That midpoint anchor is the whole idea. The classic stochastic compares the close to the lowest low, so its scale runs 0 to 100. Blau shifted the reference point to the center of the range, which is why SMI is centered on zero and runs about -100 to +100.

Blau published it in Stocks & Commodities as part of his work on double-smoothed momentum. On our charts we treat it as a bias-and-timing tool: bias from which side of zero it sits, timing from its crosses and reversals. It is not a standalone system, and no oscillator is.

Two rounds of smoothing sit on top of that midpoint calculation. That extra smoothing is the reason SMI whipsaws less than raw stochastic on noisy intraday charts, which matters if you trade M15 or M5 gold.

How the SMI formula works

Start with the range. Over your lookback (say 10 or 13 bars), find the highest high and the lowest low. The midpoint is halfway between them, and half the range is the distance from midpoint to either edge.

Now take the difference between the current close and that midpoint. If the close is above the midpoint, this number is positive; below, it is negative. That difference is the raw momentum signal, the numerator.

Here is the part that separates SMI from stochastic. Blau smooths that close-minus-midpoint difference twice with EMAs (typically two passes of about 3 periods each), and he smooths the half-range the same way, twice. So both the top and the bottom of the fraction get double-smoothed before you divide.

Divide the double-smoothed numerator by the double-smoothed half-range, multiply by 100, and you get the SMI line scaled to roughly -100 to +100. A signal line, usually a 3-period EMA of the SMI itself, gets plotted on top for cross signals.

You do not need to compute any of this by hand. The stochastic momentum index calculator will run the numbers for a series of closes so you can see how a setting change moves the output before you touch your live chart.

The takeaway without the arithmetic: SMI measures distance from the center of the range, not distance from the bottom, and it filters that measurement twice. Center reference plus double filter equals a smoother, more symmetric oscillator.

SMI vs the classic stochastic oscillator

The two look similar on a chart but they are measuring different things, and mixing up their levels is where traders get burned. Here is the clean comparison.

The scale difference is the trap. A stochastic reading of 20 is oversold, but on SMI 20 is a positive number sitting in bullish territory. If you carry stochastic habits onto an SMI pane, you will read signals backward.

Because SMI is double-smoothed, it tends to give fewer signals and fewer false ones, but it also arrives a touch later. That is the trade you are accepting: cleaner reads for slightly slower turns.

If you want the classic version alongside it for comparison, we cover setup and settings in the MT4 stochastic indicator and MT5 stochastic indicator guides. Running both panes for a week is the fastest way to feel how much quieter SMI is.

SMI settings that actually matter

Four inputs drive the SMI, and most platform defaults are reasonable starting points. Do not chase exotic numbers; the timeframe you trade matters more than a one-period tweak.

%K length (lookback): commonly 10 or 13. Shorter (say 8) reacts faster and fires more; longer (say 21) is calmer and better for swing reads on H4 and Daily. On H1 majors, 13 is a reasonable home base.

Smoothing periods: the two EMA passes are usually 3 and 3. Raising them to 5 and 3 smooths further if your chart is choppy; dropping toward 2 makes the line jumpier and defeats the point of using SMI over stochastic.

Signal line: a 3-period EMA of the SMI. Some traders push it to 5 for slower, more deliberate crosses. On M5 and M15 a 5-period signal cuts down on the constant back-and-forth.

Overbought / oversold levels: +40 / -40 is the common pair, and +50 / -50 is a stricter alternative that flags only harder extremes. On strongly trending instruments, widen toward +/-50 or the bands become useless because price camps inside them.

Timeframe notes from our own charts: on M15 majors, %K 13 with 5/3 smoothing and a 5-signal keeps the noise down. On H1 and H4, the standard 13 with 3/3 and a 3-signal is enough. On the Daily, a 21 lookback turns SMI into a slow trend-bias line rather than a timing tool.

How to read and trade the SMI

There are four workhorse signals, and each is worth more with confirmation than alone. Treat SMI as one voice, not the verdict.

Zero-line cross. SMI crossing above zero says closes have moved into the upper half of the range, a bullish shift in bias; crossing below says the opposite. This is the cleanest read of trend bias and pairs well with a moving-average or structure filter.

Overbought / oversold. Above +40 warns the move may be stretched; below -40 warns the downside may be stretched. These are warnings, not sell and buy buttons, because a strong trend can pin SMI in the zone for many bars.

Signal-line cross. When SMI crosses its own EMA signal line, that is your earlier, faster trigger. A signal-line cross back down from above +40 is a common short setup; a cross up from below -40 is a common long. Confirm with the zero line or price structure.

Divergence. Price makes a higher high while SMI makes a lower high (bearish divergence), or price makes a lower low while SMI makes a higher low (bullish). Divergence flags weakening momentum, though it can persist for a long time before price turns. Our divergence cheat sheet walks through the reliable versus the wishful patterns.

Where SMI fails is the same place every oscillator fails: strong trends. In a clean uptrend, SMI can hold above +40 and keep printing signal-line crosses that look like shorts and get run over. When the trend is obvious, favor zero-line and divergence reads over fading the extreme.

A concrete read on H1 EUR/USD: SMI tags -40, then crosses its signal line up, then pushes back above zero while price holds a higher low. Three steps in agreement, an oversold stretch, momentum turning, and bias flipping bullish, is a cleaner long than any one of those signals taken alone.

On gold (XAU/USD), this failure mode is severe. During a trending gold session, SMI can sit pinned in overbought or oversold for hours while price grinds far further in the trend direction. Do not fade a pinned SMI on gold, and size any stop in price distance, dollars per ounce, not pips, since gold’s daily swings dwarf a normal FX pip stop.

Common mistakes traders make

• Reading SMI on the stochastic scale. SMI runs -100 to +100 with zero at the center; 20 is bullish here, not oversold. Carrying 80/20 habits onto an SMI pane reverses your signals.
• Fading overbought and oversold in a trend. SMI can stay above +40 or below -40 for many bars during a strong move. Blindly shorting every OB print in an uptrend is how accounts bleed, especially on trending gold.
• Over-tightening the smoothing. Dropping the EMA passes toward 2 to get faster signals throws away the double-smoothing that made you pick SMI over raw stochastic in the first place.
• Trading every signal-line cross. On M5 and M15 the SMI crosses its signal line constantly. Without a higher-timeframe bias filter, most of those crosses are noise.
• Treating divergence as a timer. Divergence flags weakening momentum, not the exact turn. Price can hold a divergence for many bars; wait for a break of structure or a zero-line confirmation.
• Using one setting on every timeframe and instrument. A 13/3/3 that behaves on H1 EUR/USD is too jumpy on M5 gold. Match lookback and smoothing to the noise of the chart you are on.

SMI indicators for MT4 and MT5

MetaTrader does not ship SMI as a built-in, so you load a custom indicator. For MT5 the closest to Blau’s original is the Blau SMI indicator for MT5, which plots the SMI line and its signal EMA in a separate pane with the standard inputs exposed.

If you want on-chart alerts rather than reading the pane yourself, the SMI with arrows for MT4 marks signal-line crosses with arrows. Treat those arrows as prompts to look, not as a trade command, and confirm each against structure and the zero line.

One honest note on any “no-repaint” or “100% accurate” claim you see attached to an SMI arrow indicator: SMI is EMA-based, and the current bar’s value updates until the bar closes. Signals on the forming bar can shift. The only way to know an indicator does not repaint is to watch a closed-bar signal and confirm it stays put; take the marketing claim as unverified until you have done that.

Before you rely on any settings on live money, run a handful of closes through the stochastic momentum index calculator so the number on your chart matches what you expect from the inputs.

Frequently asked questions

Is the Stochastic Momentum Index better than the normal stochastic?

Not better, different. SMI is double-smoothed and centered on zero, so it whipsaws less and reads cleaner on noisy charts, at the cost of arriving slightly later. If constant false stochastic signals frustrate you, SMI is worth a trial. Neither one is a system by itself.

What are the best SMI settings for day trading?

A reasonable starting point is %K 13, smoothing 3 and 3, signal 3, with +40 / -40 bands. On fast charts like M5 and M15, raise smoothing to 5/3 and the signal to 5 to cut noise. Test on a demo before trusting any setting live; the right numbers depend on your instrument’s volatility.

What do the +40 and -40 levels mean on SMI?

They are overbought and oversold thresholds on the -100 to +100 scale. Above +40 suggests the up-move may be stretched; below -40 suggests the down-move may be stretched. They are warnings, not automatic entries, because a strong trend can hold SMI beyond those levels for a long stretch.

Does the SMI repaint?

The SMI is EMA-based, so the value on the currently forming bar can still change until that bar closes. Closed-bar readings are fixed. Any indicator claiming it “never repaints” should be checked by watching closed-bar signals yourself; take the claim as unverified until then.

Can I use SMI on gold (XAU/USD)?

Yes, but with care. During trending gold sessions SMI can sit pinned in overbought or oversold for hours while price runs far further. Do not fade a pinned SMI on gold, lean on zero-line and divergence reads instead, and set stops in dollars per ounce, not pips.

What is a good confirmation to pair with SMI signals?

Structure and a higher-timeframe bias. Use a zero-line cross or a moving average to confirm trend direction, then take signal-line crosses only in that direction. A break of a swing high or low adds weight to a divergence read. One filter turns most of SMI’s noise into skippable signals.

Trading forex and CFDs carries a high level of risk and is not suitable for everyone. Most retail traders lose money. Nothing here is financial advice; it is educational content only. Always do your own analysis and never risk money you cannot afford to lose.