Chain Wear & Stretch Calculator
Measure a span of your chain with a ruler or calipers and get the exact percent elongation, checked against the replacement limit for your chain type.
Chain & Measurement
Limit: 0.5%- Pitch
- 12.7 mm
- Pin Ø
- 3.6 mm
- Roller Ø
- 7.75 mm
12 inch ruler test (24 links)
Put the 0 mark of a metal ruler on a pin center with the chain under tension, then read how far the pin 12 inches along sits from the 12 inch mark. Tap your reading:
Measured Chain Stretch
0.52%
Service limit:0.50%
Absolute Stretch
+1.59mm
Nominal 24P:304.8 mm
Wear Life Used
104%Replace Now
Pin-to-pin length:306.39 mm
Service limit reached.
Wear gauge (0 to 1% elongation)
11/128" (9–12 Spd) reference readings (24 pitches)
| Elongation | Reading (mm) | Reading (in) | Status | Try |
|---|---|---|---|---|
| 0.00% | 304.8 | 12" | Within limit | |
| 0.50% | 306.32 | 12.06" | Replace | |
| 0.75% | 307.09 | 12.09" | Replace | |
| 1.00% | 307.85 | 12.12" | Replace | |
| 1.50% | 309.37 | 12.18" | Replace | |
| 2.00% | 310.9 | 12.24" | Replace |
How to Calculate Chain Elongation
Chain "stretch" is wear inside each joint, which lengthens the pitch. Measure a span of several pitches, because the error adds up and is easier to read. Once the chain is due, work out the replacement length with the chain length calculator, or identify an unmarked chain from its measured pitch with the caliper roller chain size calculator. Bicycle chains have their own sizing rules in the bike chain length calculator.
Caliper formulas
N is the number of pitches, P the pitch, and M your caliper reading. The corrections convert the jaw position to a true pin-center length.
Bicycle 12 inch ruler marks
24 links of 1/2 inch pitch measure exactly 12 inches when new.
- 12"0%
- 12-1/32"0.26%
- 12-1/16"0.52%
- 12-3/32"0.78%
- 12-1/8"1.04%
- 12-3/16"1.56%
Chain Wear Limits by Chain Type
The limits below are the ones this calculator uses. Industrial roller chain makers publish 1.5% for fixed-center drives and up to 3% where the center distance can be adjusted, so treat 1.5% as the conservative figure. For a motorcycle, your owner's manual's length limit takes priority.
| Chain | Pitch (mm) | Limit | 20 pitches, new (mm) | 20 pitches at limit (mm) |
|---|---|---|---|---|
| 11/128" (9–12 Spd) | 12.7 | 0.50% | 254.00 | 255.27 |
| 1/2" × 3/32" | 12.7 | 0.75% | 254.00 | 255.91 |
| 520 | 15.875 | 1.00% | 317.50 | 320.68 |
| 428 | 12.7 | 1.20% | 254.00 | 257.05 |
| #40 | 12.7 | 1.50% | 254.00 | 257.81 |
| #60 | 19.05 | 1.50% | 381.00 | 386.71 |
A badly worn chain wears sprockets too. After a replacement, compare gearing with the motorcycle sprocket calculator or, on a fixed gear, plan your skid patches with the fixie skid patch calculator.