Keep interpolation and extrapolation separate in a length correction.
What assumption is added when a reading falls beyond both references?
Use the matching calculator
Use this decision sequence
- Use two indicated readings and their independently known reference lengths.
- Check that both reading and actual-reference pairs increase.
- Apply the same entered linear relationship to the new reading.
- Flag readings outside the two reference readings rather than implying verified accuracy.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| Interpolation | Uses a reading between the two reference points. |
| Extrapolation | Extends their assumed linear relationship outside that range. |
| Calibration certification | Needs evidence absent from two entered pairs. |
Worked comparison
Indicated readings of 1 m and 3 m paired with known lengths of 1.1 m and 3.3 m imply a factor of 1.1. A 2 m reading interpolates to 2.2 m; a 4 m reading extrapolates to 4.4 m. The second result assumes the same linear relationship continues beyond the supplied references.
Check before using the estimate
No calibration procedure, instrument accuracy, acceptance tolerance or measurement certification is supplied. The example values are illustrative arithmetic inputs. Replace them with your measured plan, selected product information and actual quote where relevant.
All dimensions, product properties, prices and specifications in this example are illustrative arithmetic inputs. Use the values from your measured plan, selected product data sheet and supplier quote. This guide does not choose construction specifications or certify safety.
Calculation and scope checked 2026-10-04. Methods and scope.