Calibration SuiteCalibration Error & Tolerance
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Calibration Error & Tolerance Calculator

Compare As-Found and As-Left readings against the instrument tolerance.

1

Instrument range

Enter the calibrated engineering range.

Span100.000 PSI
2

Test point

Select a common point or enter the expected value.

3

Allowed tolerance

Choose how the instrument specification is stated.

4

Measured readings

Enter the values before and after adjustment.

Final calibration resultPASSBased on the As-Left reading
Allowed deviation at this point±0.500 PSI 0.500% of the 100.000 PSI span
As-Found50.800 PSI
FAIL
Signed error
+0.800 PSI
Absolute error
0.800 PSI
Error of span
+0.800%
Error of reading
+1.600%
As-Left50.200 PSI
PASS
Signed error
+0.200 PSI
Absolute error
0.200 PSI
Error of span
+0.200%
Error of reading
+0.400%
Δ

Error reduced by 75.000%Adjustment brought the instrument within tolerance.

Equation guide

How calibration error and tolerance are calculated

Calibration error is the difference between the measured indication and the expected reference value at a test point. The signed error shows whether the instrument reads high or low; absolute error is used for tolerance evaluation. Always apply the tolerance basis stated by the manufacturer or approved calibration procedure.

As-Found results document the condition before adjustment. As-Left results document the condition returned to service, which is why this calculator bases its final result on the As-Left reading.

Signed and absolute error

Signed error = Measured value − Expected valueAbsolute error = |Signed error|

A positive result indicates a high reading; a negative result indicates a low reading.

Percent error

Error (% span) = Error ÷ (URV − LRV) × 100Error (% reading) = Error ÷ Expected value × 100

Percent of reading is not meaningful when the expected value is zero.

Allowed deviation

Allowed deviation = Span × Tolerance % ÷ 100

For percent-of-reading tolerance, replace span with the absolute expected value. For a fixed tolerance, the entered engineering-unit value is used directly.

Pass or fail

Pass when |Measured − Expected| ≤ Allowed deviation

A value exactly on the allowable limit passes. Confirm rounding requirements before recording the result.

Worked example: 0–100 PSI instrument

At the 50 PSI test point, a ±0.5% of span tolerance allows ±0.500 PSI.

As-Found50.800 PSI → +0.800 PSI → Fail
As-Left50.200 PSI → +0.200 PSI → Pass
Error reduction(0.800 − 0.200) ÷ 0.800 = 75%

Calibration error FAQs

What is the difference between percent of span and percent of reading?

Percent of span uses the full calibrated range as its denominator, so the allowed engineering-unit error stays constant across the range. Percent of reading changes with the expected value and becomes smaller near zero.

Should final pass or fail use As-Found or As-Left?

As-Found describes how the instrument was discovered. As-Left describes its condition after any adjustment and normally determines whether it is acceptable for return to service, subject to the governing procedure.

Does a reading on the tolerance limit pass?

This calculator treats equality with the limit as a pass. Your procedure may prescribe additional guard banding or decision rules, so verify those requirements first.

Is this calculator a calibration certificate?

No. It supports field calculations but does not replace an approved procedure, traceable reference standard, uncertainty analysis, or completed calibration record.