The ATR Calculator turns a paste of price bars into a volatility number: the Average True Range, smoothed the way J. Welles Wilder defined it. You paste one high, low, close triplet per line, pick the period, and press the Calculate ATR button. The tool answers with the current ATR, a color-coded volatility assessment, and a day-by-day table of the true ranges and ATR values that built it.
Paste the bars, pick the period
The data field takes one bar per line, each line a high, a low, and a close in that order, separated by commas, semicolons, or tabs. Lines with fewer than three numbers are skipped, and a line with extra numbers contributes only its first three, so an export that keeps high, low, and close as its first three columns pastes in unchanged. The period field defaults to 14 and accepts 2 or more. Nothing happens until you press the button; the results are not live.
Enough rows or nothing at all
The guard requires at least period plus one rows. With the default period of 14 you need 15 bars; paste five and press the button and the tool shows no result, no badge, no table. Once a result exists, the table shows the last 20 rows, numbered by bar position starting at 1, and the first period minus one rows carry a dash in the ATR column, because the seed has not been reached yet. Every number in the table is printed with two decimals.
How the ATR is built
The first true range is simply high minus low. Every later true range is the largest of three: high minus low, the distance from the high to the previous close, and the distance from the low to the previous close. The first ATR, printed on row period, is the plain average of the first period true ranges. Every row after that applies Wilder smoothing: the previous ATR times period minus one, plus the new true range, divided by period. A five-bar run with period 3 shows it end to end: true ranges 2.30, 1.50, 2.10, 2.10, 2.40, and ATR values of a dash, a dash, 1.97, 2.01, and 2.14.
The volatility badge
The badge divides the final ATR by the final close and reads the percentage: above 3 percent is high volatility in red, above 1.5 percent is medium in yellow, and the rest is low in green. In the five-bar example the final ATR is 2.14 against a final close of 157.50, which is 1.36 percent, so the badge reads low. The badge describes the intensity of the movement, not its direction; ATR never says whether the price rose or fell.
What is not here, and where to go next
This tool stops at the indicator. To turn the ATR into a stop price, the ATR Stop Loss Calculator multiplies it: a long entered at 150 with an ATR of 3.5 and a multiplier of 2 gets a stop at 143.00, a risk of 4.67 percent, and a five-level table from 146.50 down to 139.50, with the short direction adding instead of subtracting. To convert that risk into a share count, use Position Sizing. To pair the volatility reading with a momentum filter, the RSI Calculator computes the oscillator from the same close prices. And when the stop and the target are set, the risk reward ratio guide turns entry, stop, and target into the ratio and the win rate the plan requires.