Skip to content
Allin
Sign up · Sign in

Percentage error calculator

Compute the percentage error between a measured and a true value.

Related tools

All Percentages & ratios tools →
Percentage difference calculatorCompute the percentage difference between two values (relative to their average).Percentage change calculatorFind the percentage increase or decrease between two numbers.Percentage decrease calculatorHow far a value fell from an old figure to a new one, as a percentage — and the absolute drop. A negative result means it actually rose.Percentage increase calculatorBy how much a value grew from an old figure to a new one, as a percentage — and the absolute change. A negative result means it actually fell.Percentage point change calculatorFind the difference in percentage points between two percentages, and the relative change.Reverse percentage calculatorFind the whole when you know that a value is a given percentage of it.Percentage calculatorFour percentage calculations in one: X% of Y, what percent X is of Y, and increasing or decreasing a value by a percentage.Standard error calculatorCompute the standard error of the mean from a list of numbers.

Need Percentage error? The Percentage error calculator derives it from Measured value, True value in one step. For instance, with Measured value = 98 and True value = 100 it returns Percentage error = 2%.

How to use it

  1. Enter your values: Measured value, True value.
  2. Read the result instantly: Percentage error.

Frequently asked questions

How does the Percentage error calculator work?

It takes Measured value and True value and derives Percentage error from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Measured value and True value. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Measured value = 98 and True value = 100, the calculator returns Percentage error = 2%. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

When would I actually use this?

The everyday cases: a discount at the till, a rise or fall between two figures, the price before tax, and working backwards from a total.

What is the most common mistake?

Undoing a percentage by applying it again. Take 20% off 100 and you get 80; add 20% to 80 and you get 96, not 100 — the two operations use different bases.

What is the difference between the Percentage error calculator and the Percentage difference calculator?

This one returns Percentage error; the Percentage difference calculator returns Percentage difference. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Percentage change calculator is the closest one after this: Find the percentage increase or decrease between two numbers.

What else is worth having open alongside it?

Percentage decrease calculator and Percentage increase calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from, and how current are they?

Percentage arithmetic is exact and universal. Where a result is a rate rather than an amount, the tool states the base it was taken on, because that is where the ambiguity lives.

Further reading

All guides →
How-toHow to Calculate Percent Error: The Accuracy Formula for SciencePercent error tells you how close a measurement is to the true value. Learn the formula, work through an example, and see how scientists use it to judge accuracy.ExplainerPercentage Difference vs. Percentage Change vs. Percentage ErrorThree percentages that look alike but answer different questions. Learn the formula for each, when to use it, and why they give different numbers.How-toHow to Calculate a Percentage: 4 Methods with ExamplesA clear guide to percentages: find X% of a number, work out what percent one number is of another, and add or subtract a percentage — with worked examples.How-toPercentage Change: Increase and DecreaseSubtract old from new, divide by the old value, times 100. Here's the formula, why increases and decreases aren't symmetric, and where it's used.ExplainerPercentage Points Are Not PercentMoving from 4% to 5% is a rise of one percentage point and a rise of twenty-five percent. Both statements are true, which is exactly why the ambiguity is so easy to exploit — and why basis points exist.ExplainerStacked Discounts Do Not Add UpTwenty percent off and then a further ten percent off is not thirty percent off — it is twenty-eight, because the second discount applies to the already-reduced price. The general rule, the cases where order matters, and how sales tax changes the answer.