CalcaTools

Percentile Range Calculator

Computes the spread between any two percentiles of a data set — interquartile range, P10–P90 or any custom band.

Last updated: June 2026 · Free · No sign-up required

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Results

Enter values above and click Calculate to see your result instantly.

Quick reference

DataBandValuesRange
1–10P25–P753.25 / 7.754.5
1–10P10–P901.9 / 9.17.2
15, 20, 35, 40, 50P10–P9017 / 4629
Any dataP0–P100min / maxfull range

functions Shows the working, not just the answer

For students and teachers, the final number is only half the value. Every math tool here exposes the formula it applied, the intermediate steps, and the rounding rule, so you can follow along, check your homework, or use the answer in a proof or report with confidence.

calculate Accurate to the spec

Calculations use 64-bit floating point with sensible rounding for the domain (currency to 2 decimals, percentages to 4 decimals, algebra to 6 significant figures). Where exact rational arithmetic matters — fractions, factorials, simplification — we use a dedicated BigNumber path so 1/3 + 1/6 returns ½, not 0.49999.

school Free for classroom use

Educators are welcome to link to any math calculator on CalcaTools from a class site, Google Classroom, or worksheet. The pages are mobile-friendly, free, ad-supported (so we can keep them free) and have no sign-up wall — students just click and use them in class or at home.

tips_and_updates Pair with the spoke articles

Below the calculator we link a small set of plain-English explainer pages — "What is a percentage?", "Why does PEMDAS matter?", and so on. They cover the underlying concept in 4–6 short paragraphs. Read those before the calculator if the topic is new, or after if you want the extra context.

Interpretation guide

BandWhat it captures
P25–P75 (IQR)Middle 50% — standard outlier-resistant spread
P10–P90Middle 80% — common in salary and growth charts
P5–P95Middle 90% — reference intervals in medicine
P2.5–P97.595% reference range, mirrors a 95% CI

Formula & methodology

Formula: Range = P(upper) − P(lower), percentiles by linear interpolation: h = (n−1)p/100, v = x⌊h⌋ + (h−⌊h⌋)(x⌊h⌋₊₁ − x⌊h⌋)

  1. Paste your data set — at least two numbers, any separator.
  2. Pick the lower and upper percentiles (defaults 25 and 75 give the interquartile range).
  3. Values are sorted and each percentile is found by linear interpolation between the two nearest order statistics (the R-7 method, identical to Excel's PERCENTILE.INC).
  4. The range is simply the upper percentile minus the lower.

Worked example: data 1–10 with P25 and P75 → P25 = 3.25, P75 = 7.75, interquartile range = 4.5.

Frequently asked questions

What is a percentile range?
The distance between two percentiles of a data set — for example the IQR is P75 − P25, covering the middle 50% of values while ignoring extremes on both ends.
How are the percentile values calculated?
By linear interpolation between sorted values (method R-7): position h = (n−1)p/100, then blend the two neighbors. It matches Excel's PERCENTILE.INC and NumPy's default.
Why use the IQR instead of the full range?
The full range moves with a single outlier; the IQR only looks at the middle half, so it is a robust spread measure and powers the classic 1.5 × IQR outlier fence.
What is the P10–P90 range used for?
It spans the middle 80% and is the standard band in salary surveys, pediatric growth charts and forecasting cones — wide enough to be informative, robust enough to ignore the wildest 20%.
Can I compute a single percentile with this tool?
Yes — set both bounds around the value you care about, or read the P-low / P-high rows directly; entering 50 for either bound also surfaces the median, which is always displayed.

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