How We Calculate
Every number on this site comes from a stated formula, a published standard or a manufacturer table. Here is what we use and where it stops being exact.
Formulas and Standards
Chain length
The chain length calculator uses the ASME B29.1 roller chain equation to turn the two tooth counts, the chain pitch and the center distance into a link count. The result is rounded up to an even number so no offset link is needed, and the center distance is then solved back from the rounded link count. The rear axle shift, small-sprocket wrap angle and hunting-tooth check are derived from the same geometry.
Sprocket geometry
Pitch diameter, outside diameter and chordal action come from the standard ASME B29.1 sprocket formulas. The sprocket diameter calculator draws the tooth form to that standard and its DXF export is checked with an independent DXF reader.
Ratios, speed and gearing
Gear ratio is driven teeth divided by driving teeth, compounded across stages for a jackshaft. Chain speed and vehicle speed follow from pitch, tooth count and rotational speed, with tire size where a vehicle is involved.
Chain wear
Wear is measured as elongation over a known number of pitches. The chain wear calculator compares your reading with published limits: 1.5% on fixed centers and up to 3% on adjustable centers for roller chain, and 0.5% to 0.75% for bicycle chains depending on the speed count.
Chain Data and Where It Comes From
The chain database holds dimensions, tensile strength and weight for motorcycle, ANSI, ISO, kart and bicycle chains. Each entry records its source and a data quality flag:
- Manufacturer: taken from a manufacturer table, such as the JT Drive Chain technical sheet for motorcycle chain or the Renold Jeffrey tables for ANSI and ISO chain.
- Approximate: no manufacturer table was found, so the value is typical and is labeled that way.
Bicycle chain sizing rules cite their origin too, including the SRAM Chains service manual and Park Tool chain length guidance. The bike chain length calculator applies those rules as written by the makers.
How We Test
All calculation code lives in plain TypeScript modules separate from the page layout. Each function has automated tests that check known values and round trips, such as converting a result back to its inputs. The data tables have an integrity test that catches inconsistent entries. The tests run on every change before it is published.
Worked examples on the pages are generated from the same calculation code, not typed by hand, so an example cannot drift from the tool.
Limits of Every Result
- Results are estimates for planning. Real chains vary by manufacturer and batch.
- Lubrication, load, speed and environment change real service life. Calculators show the geometry, not a guarantee of life.
- Where a manufacturer publishes its own rule, the manufacturer's rule wins. Always check the installation guide for your chain and vehicle.
See the Disclaimer for the full wording.