Indicators: MA, RSI, MACD, Bollinger
What each line is drawn from, and what that leaves out
Take a EUR/USD chart near 1.0850 and add a 20-period moving average. The line is the average of the last 20 closing prices, redrawn at every candle, so its newest value depends on a candle that is still moving. Because every value in the average is a price that has already happened, the line can only describe where price has been. It cannot contain any number that has not yet printed.
RSI is built differently. It takes the average size of recent up-closes and the average size of recent down-closes over a set number of candles, then scales the ratio onto a line between 0 and 100. Nothing in that arithmetic uses the distance price travelled, only the direction of each close and its size. A market that rises 200 pips in small steps and one that rises 200 pips in large steps can produce the same reading.
MACD subtracts one moving average from another and then smooths that difference. It is two averages compared, nothing more, so it inherits the lag of both. Bollinger Bands take a moving average and add and subtract a multiple of the standard deviation of recent closes, which is a measure of how spread out those closes were. The width of the bands is a statement about past dispersion, not about direction.
The practical consequence is the same for all four. Each line is arithmetic on closes that have already printed, so each one turns after the price move that caused it. A line that turns after the move can confirm what happened. It cannot announce what happens next.
Reading the four lines together on one chart
Open a EUR/USD chart near 1.0850 with all four indicators in separate panels below the price. The moving average sits on the price panel, the other three sit underneath. Read the price candles first, then look down at the panels. The panels describe the candles above them, not the other way round.
Suppose price has drifted sideways for two days. The moving average flattens and hugs the candles, RSI wanders near its midpoint, MACD sits close to zero, and the Bollinger Bands narrow. All four are saying the same thing: recent closes were similar to each other and to their average. That is a description of a quiet market. It is not a forecast that the quiet will continue.
Now suppose price breaks upward and closes 80 pips higher over several candles. The moving average begins to slope up, but only as the new closes replace old ones in its window. RSI rises because up-closes now dominate the recent sample. MACD widens because the short average pulls away from the long one. The bands widen because the closes are more spread out. Each panel is reacting to the same candles at its own speed.
The speeds differ, and that difference is the useful part. The moving average and MACD are slow because they average; RSI is quicker because it looks only at the recent sample of gains and losses; the bands say nothing about direction at all. When the panels disagree, the disagreement is about how much past data each one is carrying, not about a hidden message in the chart.
Where the arithmetic stops being useful
A line calculated from past closes has no way to include news, a central bank statement, or a change in the spread your broker quotes. If a scheduled release moves EUR/USD 60 pips in a minute, the indicators will show it afterwards. At 10 units of the quote currency per pip on one standard lot, 60 pips is 600 units, which at 1.0850 is about ₱651 before costs. The panels will not have warned you before that candle.
The same arithmetic also means the lines can be read in more than one way. RSI near its upper region can mean recent gains were large, and it can stay there while a trend continues. A moving average can be far from price in a fast market and close to it in a slow one. Neither reading tells you what to do. Both tell you what the recent closes looked like.
Treat each panel as a summary with a stated input. The moving average summarises closes over its window. RSI summarises the balance of recent gains and losses. MACD summarises the gap between two averages. The bands summarise how spread out recent closes were. If you cannot say which input a line is summarising, the line is decoration.
None of the four can be tested against a future you have not seen. They can be checked against the chart you already have, which is enough to see how each one behaved after a move. That check is where the value sits, and it is also where the limits show up.
One 20-pip move, four indicators
| Step | Amount | Note |
|---|---|---|
| Price move | 20 pips | EUR/USD moves from 1.0850 to 1.0870 |
| Value on one standard lot | about ₱200 | 20 pips x 10 units per pip = 200 units, converted at 1.0850 |
| Moving average | lags by half its length | a 20-period average turns after price has already moved |
| RSI | moves toward 70 | it measures the size of recent gains against recent losses |
| MACD | line crosses its signal | it compares two moving averages of price |
| Bollinger Bands | price touches the upper band | the bands widen or narrow with recent volatility |
Your broker may round the peso conversion, add a spread, and charge commission or swap, so the cash figure on your statement can differ from this estimate.
Doing it once, step by step
You will add the four indicators to one EUR/USD chart, then read each panel against the candles above it. Do this on a demo account or a chart with no order attached.
- 01
Open a EUR/USD chart near 1.0850
Use a daily or four-hour chart so each candle carries enough closes to average. Note the current price and the time of the last candle. Do not place an order.
- 02
Add a 20-period moving average
Set the period to 20 and leave the input on close. Watch how the line moves while the newest candle is still forming. Note that its last value changes until that candle closes.
- 03
Add RSI with its default period
Keep the default setting and read the line between 0 and 100. Compare a day of small up-closes with a day of large up-closes and see whether the reading differs much.
- 04
Add MACD and read the two lines
MACD draws a faster line and a slower line, plus bars for the gap between them. The bars widen when the two averages pull apart. That is a statement about the averages, not about direction.
- 05
Add Bollinger Bands and watch the width
The bands sit a set number of standard deviations above and below a moving average. Narrow bands mean recent closes were close together. Wide bands mean they were spread out.
- 06
Check each panel against the candles
Pick one past move on the chart and write down what each panel showed before, during and after it. If a panel gave no warning before the move, record that too. This is the limit of the arithmetic, seen on your own chart.
The mistake most people make here
The common mistake is to treat an indicator as a signal that tells you what to do. A moving average only averages old prices, so it turns after the move; RSI only compares recent gains and losses, so it can stay high in a strong trend; MACD only compares two averages, so it lags; Bollinger Bands only measure how spread out recent prices were. Use them to describe what has already happened on the chart, and check the price itself before acting.Check yourself
EUR/USD is at 1.0850 and moves 15 pips against you on one standard lot. What is the loss in pesos at that rate?
15 pips x 10 units per pip = 150 units of the quote currency; 150 x 1.0850 = ₱162.75, before any spread, commission or swap.
A 20-period moving average is drawn on a chart. How many past candles does it use, and does it include the current candle?
It uses the last 20 closes, and the current candle is included once it has a price, so the line changes as that candle moves.
Questions that come up next
Why does the moving average line seem to follow the price instead of leading it?
The line is the average of the last 20 closing prices. Each of those closes has already happened, so the newest value of the average is built from prices you can already see on the chart. When price turns, the average keeps some of the old closes in its sum, so it turns later. It describes the past, and the past is all it has.
Can RSI stay above 70 for a long time?
Yes. RSI compares the size of recent up-closes with the size of recent down-closes. In a steady rise, most closes are up-closes, so the reading stays high. The number is a description of what the closes did, not a warning that they must stop. A high reading can persist for as long as the closes keep behaving that way.
What does the MACD histogram show that the two lines do not?
The MACD line is one average minus another. The signal line is an average of that difference. The histogram is the gap between the two lines, drawn as bars. It shows whether the gap is widening or narrowing. It is still arithmetic on past closes, so it changes after the closes change.
If the Bollinger Bands narrow, does that mean a big move is coming?
No. Narrow bands mean recent closes were close to their average, so the standard deviation was small. That is a statement about the past. A quiet market can stay quiet, and a narrow band can widen or stay narrow. The bands measure spread, not direction, and they cannot say what happens next.
Do the four indicators ever disagree on the same chart?
They can, because each one is a different sum of the same closes. A moving average can slope up while RSI falls, if the up-closes are getting smaller. When they disagree, the chart is telling you the closes changed in a way that affects one sum more than another. Read the candles first, then the panels.
Should I add more indicators to get a clearer picture?
Adding more lines adds more sums of the same past closes. If two indicators are built from the same closes in similar ways, they will often say the same thing. The chart does not gain new information from a fifth line. What you can do is check the price itself before acting on any line.
The words used on this page
- Moving average
- A line that shows the average of the last set number of closing prices. It is redrawn at every candle, so its newest value changes while the current candle is still moving. It is arithmetic on closes that have already printed.
- RSI
- A line between 0 and 100 that compares the average size of recent up-closes with the average size of recent down-closes. It uses the direction and size of each close, not the distance price travelled. A high reading can stay high while the closes keep rising.
- MACD
- A line made by subtracting one moving average from another, then smoothing that difference. It is two averages compared, so it carries the lag of both. The histogram shows the gap between the MACD line and its signal line.
- Bollinger Bands
- A moving average with a line drawn a set distance above and below it. That distance is a multiple of the standard deviation of recent closes, which measures how spread out they were. Narrow bands mean the closes were close together, not that a move is due.
- Standard deviation
- A number that describes how spread out a set of values is. If the recent closes are all near their average, the standard deviation is small. If they are scattered far from it, the number is large. It says nothing about which way price will go.
- Lag
- The delay between a price move and the change in a line drawn from past prices. Every indicator on this page has it, because each one is built from closes that have already happened. A line that turns after the move can confirm what happened, not announce what comes next.
What to take away
- Each of the four indicators is arithmetic on closes that have already printed, drawn as a line.
- A moving average averages old closes, RSI compares recent gains and losses, MACD compares two averages, and Bollinger Bands measure how spread out recent closes were.
- Every one of them turns after the price move that caused it, so none can announce what happens next.
- Read the price candles first, then the panels below them, and check the price itself before acting.