Percent Tolerance Calculator

Frequently asked questions

What is percent tolerance?

Percent tolerance states how far a measured value may deviate from its nominal value, as a percentage of the nominal. With nominal N and tolerance ±t%, the accepted range is min = N × (1 − t) and max = N × (1 + t). Example: a 100 Ω resistor rated ±5% is accepted between 100 × 0.95 = 95 Ω and 100 × 1.05 = 105 Ω.

How do you calculate the tolerance range?

Multiply the nominal by (1 − tolerance) for the minimum and by (1 + tolerance) for the maximum, with tolerance as a decimal. For 100 ±5%: min = 100 × 0.95 = 95, max = 100 × 1.05 = 105.

What is 5% tolerance on a 4.7 kΩ resistor?

min = 4.7 × 0.95 = 4.465 kΩ and max = 4.7 × 1.05 = 4.935 kΩ — the resistor is within specification anywhere between 4.465 kΩ and 4.935 kΩ.

How do you find the nominal value and tolerance from min and max?

Work backwards: nominal = (min + max) ÷ 2, and tolerance% = (max − min) ÷ (max + min) × 100. Example: limits 95–105 give nominal (95 + 105) ÷ 2 = 100 and ±(10 ÷ 200) × 100 = ±5%.

What do 0% and 100% tolerance mean?

0% tolerance means the value must equal the nominal exactly: 100 ±0% gives 100–100. 100% tolerance means the lower limit reaches zero: 100 ±100% gives 0–200.

What is the difference between percent and absolute tolerance?

Percent tolerance scales with the nominal value (±5% of 100 is ±5), while absolute tolerance is a fixed amount. Example: 25.4 mm ±0.1 gives 25.3–25.5 mm, which equals ±0.3937%.

Why do resistors and machined parts use tolerance bands?

No manufacturing process is perfect, so parts are specified with a nominal value plus a tolerance band that the real value must fall inside. Standard resistor series use 1%, 2%, 5% and 10% bands; machining drawings often use absolute tolerances like ±0.1 mm.

What happens with a zero nominal value?

Any percent tolerance of zero is still zero: 0 ±5% gives 0–0, so percent tolerance is meaningless at a zero nominal — use absolute tolerance (for example ±0.1) instead.