How Technical Indicators Are Calculated: From Price and Volume to a Plotted Line

In short: Every indicator is just a formula that takes a window of past price or volume data — usually open, high, low, close and volume — and reduces it to one or more numbers that are plotted bar by bar.

It all starts with OHLCV

Every indicator on your chart is built from the same raw ingredients: the open, high, low and close of each bar, plus volume. Nothing else. A moving average averages the closes; RSI compares up-closes to down-closes; ATR measures the high-to-low range; VWAP weights price by volume. When you understand that an indicator is only a recipe applied to these five numbers, it stops being a black box. There is no hidden data feed and no secret — just arithmetic repeated on every new bar as it forms.

The look-back window

Almost every indicator uses a look-back period — the '14' in RSI(14) or the '20' in a 20-day moving average. This window decides how many past bars the formula sees. A short window reacts fast but is noisy; a long window is smooth but slow. On a Nifty daily chart, a 20-day average captures roughly a trading month; a 50-day captures a quarter. The window is the single most important choice you make, because it sets the trade-off between responsiveness and reliability that defines how the indicator behaves.

Smoothing: turning jagged data into a line

Raw price is jagged, so most indicators smooth it. The three common methods are the simple moving average (equal weight to every bar), the exponential moving average (more weight to recent bars), and Wilder's smoothing (a slower exponential method used in RSI, ATR and ADX). Smoothing is what turns a cloud of dots into a readable curve, but it always adds lag — the smoother the line, the further behind price it sits. Every indicator is a compromise between smoothness and lag.

Two families: overlays and oscillators

Once the maths is done, the result is plotted in one of two ways. Overlays sit on the price chart in the same units as price — moving averages, Bollinger Bands, VWAP, Supertrend. Oscillators sit in a sub-panel below, on their own scale — RSI and Stochastic on 0 to 100, MACD around a zero line, CCI around zero. Knowing which family an indicator belongs to tells you how to read it: overlays for levels and trend, oscillators for momentum and extremes.

Normalisation and bounded scales

Some formulas deliberately squeeze their output into a fixed range so it is easy to compare across instruments and time. RSI and Stochastic are normalised to 0–100; Williams %R to −100 to 0. This is why an RSI of 70 means the same 'stretched' thing on Nifty as on Reliance, even though their prices differ by thousands of rupees. Unbounded indicators like MACD or CCI have no such ceiling, so their values are only meaningful relative to that instrument's own history.

Why the same indicator can look different

Two charts can show 'RSI(14)' yet not match, because platforms differ in small ways: which smoothing they use, whether the current bar is included, how they handle the first few bars before the window fills, and whether they compute on close or on live price. These differences are usually tiny, but they explain why your broker's RSI and TradingView's RSI can disagree by a point. It also reminds you that an indicator value is a construction, not a fact of nature.

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Published 14 January 2026. Educational content only — not investment advice.