Measurement math · Symmetric limits
Percent Tolerance Calculator
Enter a target value and a ± tolerance percentage to find the lower limit, upper limit, absolute tolerance and total range width. Use the same unit for the target and all results.
Your specification
For ±5%, enter 5. Use a tolerance specified for your task; this calculator does not choose it for you.
Tolerance limits
- Lower limit
- 209
- Upper limit
- 231
- Absolute tolerance (±)
- 11
- Range width
- 22
Results use the target’s unit and are displayed to at most 12 significant digits. Values very close to a limit may require higher precision.
How the limits are calculated
Absolute tolerance = |target| × tolerance % ÷ 100
Lower = target − absolute tolerance
Upper = target + absolute tolerance
Range width = 2 × absolute tolerance
For a positive target, this is target × (1 − tolerance / 100) and target × (1 + tolerance / 100). At a target of 220 and ±5%, the allowance is 11, the limits are 209 and 231, and the full width is 22.
A negative target of −50 with ±2% has an allowance of 1 and limits of −51 and −49. A tolerance of 0% produces a single value. Percentages above 100% are mathematically supported, but a negative lower limit may not be meaningful for a physical quantity such as mass.
Tolerance is not percent error
Tolerance starts with an allowance and finds a range. Percent error starts with a measured and reference value and describes their difference. A general percentage calculator performs arithmetic; this tool returns both bounds and the band width together.
This tool evaluates symmetric percentage limits only. It does not look up ISO fits, process capability, uncertainty budgets or industry acceptance rules. Use your own specification and measurement procedure; the result is not a certification of compliance.
Formula reference: CalculatorSoup’s percent tolerance formulas, including the magnitude-based formula for negative values.
About This Calculator
Find upper and lower limits from a target value and a plus/minus percent tolerance. See the absolute allowance and full range width, including negative targets.
Frequently Asked Questions
How do I calculate percent tolerance limits?
Multiply the magnitude of the target by tolerance divided by 100. Subtract this allowance from the target for the lower limit and add it for the upper limit.
Does this calculator support negative or zero targets?
Yes. A negative target uses its magnitude for the allowance. For a zero target, any percentage allowance is zero; use an absolute specification if a nonzero allowance is intended.
Does this select an engineering tolerance standard?
No. Enter the tolerance from your own specification. This is symmetric percentage math, not an ISO fit lookup, measurement uncertainty assessment or certification.
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