RSI and MACD explained: what momentum indicators measure and how they are misused

RSI and MACD are momentum indicators: they measure how fast and how persistently price has been moving, using nothing but past closing prices. RSI condenses recent gains and losses into a 0 to 100 scale; MACD tracks the gap between a fast and a slow exponential moving average. They can help describe whether a move is gaining or losing strength, but they are not forecasts, and their best-known signals, overbought, oversold, crossovers and divergence, fail often.

What momentum indicators are trying to measure

Momentum is the speed of a price move. If a pair rises 20 pips a day for ten days, momentum is strong and steady. If it then rises only 5 pips a day, price is still going up, but momentum has slowed.

The idea behind momentum indicators is that changes in speed can sometimes come before changes in direction, just as a car slows before it turns. The analogy is useful and also misleading: a car that slows might simply keep going slowly, and markets can switch direction without slowing at all, for example on a surprise central bank decision.

Both indicators below are derived purely from price. That matters. They do not see order flow, positioning, interest rates or news. Anything they show is already visible on the price chart, just presented differently. If you are new to reading charts, start with how to read candlestick charts.

RSI: the Relative Strength Index

Where it comes from

RSI was introduced by J. Welles Wilder in his 1978 book New Concepts in Technical Trading Systems. Wilder's default look-back was 14 periods, and that remains the most common setting.

How it is calculated

In plain terms:

1. For each period, measure the change from the previous close. Separate the gains (up closes) from the losses (down closes).
2. Calculate the average gain and the average loss over the look-back period. Wilder used a particular smoothing method, similar to an exponential average, so recent periods count a bit more.
3. Divide the average gain by the average loss. This is the relative strength, RS.
4. Convert to a 0 to 100 scale: RSI = 100 minus (100 divided by (1 + RS)).

Worked example

Illustrative numbers: over the last 14 days, a pair's average daily gain on up days was 30 pips and its average daily loss on down days was 15 pips. RS = 30 / 15 = 2. RSI = 100 minus (100 / 3) = 100 minus 33.3 = 66.7.

If instead the average gain was 15 and the average loss 30, RS = 0.5 and RSI = 100 minus (100 / 1.5) = 33.3. If gains and losses were equal, RS = 1 and RSI = 50.

Notice what RSI is: a ratio of recent up moves to recent down moves. An RSI of 66.7 means recent gains have been roughly twice the size of recent losses. That is all. It does not know whether the move is driven by a temporary flow or a fundamental change in interest-rate expectations.

Overbought and oversold

Readings above 70 are conventionally called overbought and below 30 oversold. Those words are among the most misleading in trading. Overbought does not mean too expensive or about to fall. It means price has risen strongly and consistently over the look-back period.

In a powerful uptrend, RSI can sit above 70 for weeks, and selling every time it crosses 70 can produce a long series of losses. In a downtrend, the same is true below 30. Some traders adapt by watching the 40 to 80 range in uptrends and 20 to 60 in downtrends, or by treating a strong RSI as a sign of trend strength rather than a reason to fade it. Neither adjustment turns RSI into a forecast.

The 50 line

Some traders use RSI above or below 50 as a simple momentum filter: above 50, recent gains outweigh recent losses. This is similar to checking whether price is above a short moving average. It is a description, not a prediction.

MACD: Moving Average Convergence Divergence

Where it comes from

MACD was developed by Gerald Appel in the late 1970s. The standard settings are 12, 26 and 9.

How it is calculated

1. MACD line = 12-period EMA of price minus 26-period EMA of price.
2. Signal line = 9-period EMA of the MACD line.
3. Histogram = MACD line minus signal line.

If exponential moving averages are new to you, read trend following and moving averages first. MACD is essentially a moving-average crossover system in a different shape. When the fast EMA is above the slow EMA, MACD is positive. When the gap is widening, momentum is increasing; when it is narrowing, momentum is fading.

Worked example

Illustrative numbers on EUR/USD: the 12-period EMA is 1.0950 and the 26-period EMA is 1.0920. The MACD line is 1.0950 minus 1.0920 = 0.0030, which is 30 pips. If the signal line, a smoothed version of recent MACD values, is 0.0022, the histogram is 0.0008, or 8 pips.

What does that tell you? The short-term average is 30 pips above the longer-term average, so price has been rising, and the gap is larger than its own recent average, so the upward momentum has been increasing. If over the next few days the histogram shrinks from 8 pips to 3 to zero, momentum is fading, even though MACD is still positive and price may still be rising.

Note that MACD is measured in price units. A MACD of 0.0030 on EUR/USD and 0.30 on USD/JPY are not comparable, and the same pair's typical MACD values change with volatility. That makes fixed thresholds on MACD much less meaningful than on RSI.

Common MACD signals

• Signal line crossover: MACD crosses above its signal line (often read as bullish momentum) or below it (bearish).
• Zero line crossover: MACD crosses above or below zero, which simply means the 12 EMA has crossed the 26 EMA.
• Histogram turning: the histogram shrinking towards zero shows momentum fading.

All three are versions of moving averages crossing, so they share the same structural problem: in trending markets they catch part of the move late, and in sideways markets they cross back and forth and produce repeated small losses.

Divergence: what it is and why it misleads

Divergence is when price and an indicator disagree. Bearish divergence is when price makes a higher high but RSI or MACD makes a lower high. Bullish divergence is a lower low in price with a higher low in the indicator.

What divergence really shows: the latest push in price was weaker than the previous one. That is genuine information about momentum. It is not a sign that price will reverse. Trends often show divergence several times as they continue, because a steady trend naturally has smaller impulses than its first burst.

Illustrative scenario: GBP/USD makes a high at 1.3000 with RSI at 78. It pulls back and then rallies to 1.3060, a higher high, but RSI reaches only 71. That is bearish divergence. A trader who sells at 1.3060 on the divergence and places a stop at 1.3100 might see price pull back 50 pips, or might see price grind on to 1.3200 with RSI diverging twice more. The indicator looked the same in both outcomes. Only the stop and the position size decide how much the second outcome costs.

Divergence also depends on which peaks you choose to compare, and charts viewed with hindsight make the textbook examples look obvious. When tested systematically, without cherry-picking, signals are much noisier.

Why RSI and MACD together are not double confirmation

A common approach is to wait until RSI and MACD agree, on the theory that two signals are stronger than one. The problem is that both are calculated from the same closing prices over overlapping periods. When price has risen strongly for two weeks, RSI will be high and MACD will be positive almost automatically. Their agreement is largely mechanical, not independent evidence.

Genuinely different information comes from different sources: the economic backdrop (see how economic data moves forex and central banks and interest rates), market structure (see support and resistance), or the calendar of scheduled events (see how to use an economic calendar). Even these do not combine into certainty; they just give you more to think about.

Settings, timeframes and the overfitting trap

Changing the settings changes the behaviour. A shorter RSI (say 7) swings more often into extreme territory; a longer one (21) rarely does. A faster MACD (for example 5, 35, 5 has been used by some traders) reacts earlier with more noise.

It is tempting to search for the settings that would have worked best on a past chart. With enough combinations, you will always find something that looks impressive in hindsight and does worse afterwards. That is overfitting, and it is explained in how to backtest a strategy. If you change a setting, have a reason other than "it fitted last year better".

Timeframe matters too. RSI on a five-minute chart and RSI on a daily chart describe completely different things. A daily overbought reading may coincide with an oversold reading on the 15-minute chart. Neither is wrong; they measure different windows.

Where momentum indicators can genuinely help

Used carefully, they can be informative:

• Describing conditions. RSI around 50 with a flat MACD near zero is a decent description of a market without much momentum, which may be useful if you trade ranges or want to avoid them.
• Spotting fading moves. A shrinking MACD histogram or a lower RSI peak can prompt you to review an open position, tighten a plan or take partial profits according to rules you set in advance.
• Consistency. A precise, written rule using an indicator is easier to test and to follow than a vague feeling. That is a process benefit rather than a predictive one.

Whatever role an indicator plays, the parts of the plan that determine survival are separate: where the stop goes, how big the position is and how much of the account is at risk. See where to put a stop-loss, position sizing and risk-reward ratio.

Worked example: a rule and its risk

Illustrative only. Suppose a trader writes this rule for a daily EUR/USD chart: in an uptrend (price above a rising 200-day average), buy when RSI dips below 40 and then closes back above it; stop-loss 20 pips below the recent swing low; exit when RSI closes above 70 or the stop is hit.

On one occasion, the signal triggers at 1.0870 and the swing low is at 1.0820, so the stop goes at 1.0800, 70 pips away. With a EUR 10,000 account and a 1% risk limit (EUR 100), and with one mini lot on EUR/USD worth about $1 per pip (roughly EUR 0.92 at an illustrative rate), 70 pips is about EUR 64 per mini lot. One mini lot keeps risk under EUR 100; two would breach it. The indicator only found the entry. The sizing decision, made using the method in lot sizes and position sizing, is what decides whether being wrong is affordable.

And it will be wrong regularly. A rule like this needs dozens of recorded outcomes before you have any idea of its behaviour, which is what a trading journal is for.

Common mistakes

• Selling because RSI is above 70. Overbought describes strength, not exhaustion.
• Treating divergence as a reversal signal. It is a momentum observation that can persist for a long time.
• Indicator stacking. Adding stochastics, CCI, RSI and MACD to one chart produces four views of the same data.
• Ignoring the trend. Oscillator signals against a strong trend are especially unreliable.
• Ignoring news. No indicator anticipates a central bank surprise. A momentum reading can be irrelevant ten seconds after a data release.
• Forgetting costs. Frequent signals mean frequent spreads and commissions; see spreads and commissions.
• Using leverage to make small signals worthwhile. Leverage magnifies losses as well as gains. Most retail CFD accounts lose money; see leverage and margin and why most retail CFD traders lose.

Frequently asked questions

What does RSI measure?

RSI measures the size of recent up moves relative to recent down moves, scaled from 0 to 100. A high reading means gains have dominated over the look-back period; a low reading means losses have. It does not measure value or predict direction.

What are the standard RSI and MACD settings?

RSI is usually set to 14 periods with levels at 70 and 30. MACD normally uses 12 and 26-period EMAs with a 9-period signal line. These are conventions, not optimal values.

Is RSI above 70 a sell signal?

Not by itself. It means price has risen strongly recently. In strong uptrends, RSI can stay above 70 for long periods while price keeps rising, so treating it as an automatic sell signal can lead to repeated losses.

What is MACD divergence?

It is when price makes a new high or low but MACD does not. It shows that the latest move had less momentum than the previous one. Trends often continue despite divergence, so it is not reliable as a reversal signal on its own.

Which is better, RSI or MACD?

Neither is better; they describe momentum in different ways. RSI is bounded between 0 and 100, which makes extremes easy to see. MACD shows the relationship between two moving averages in price terms, which suits trend analysis. Both lag and both fail often.

Can I trade with RSI and MACD alone?

You can build a rule around them, but an indicator is only one part of a plan. Position sizing, stop placement, costs and awareness of scheduled news determine how much a losing trade costs, and every approach has losing trades.