A worked example
2100 mm circumference, 50/25 gearing and 90 rpm give 22.68 km/h.
SPINKIND / EVERYDAY TOOLS
Find your rhythm.Understand your gears.
Compare gearing, cadence and measured wheel rollout with simple transparent calculations.
Make a little plan✓ Free to use✓ No uploads✓ Ready to print
MEASURE / PLAN / MAKEA clearer plan starts here.
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YOUR LITTLE WORKBENCH
ON YOUR DEVICE ✦Gear speed
Loading your local workspace…
THE METHOD / 01
A clear wayfrom start to finish.
km/h = circumference in mm × front/rear × cadence × 60 ÷ 1,000,000.
Keep the assumptions clear
Ideal drivetrain only; no wind, gradient, power or real-world speed prediction.
A FEW USEFUL ANSWERS
Good to know.
Are my inputs uploaded?
No. Processing runs locally in your browser. The host still receives normal requests for website pages and assets.
Can I keep my result?
Use the download controls for the current tool or print from your browser. Your valid edits autosave in this browser. Export a JSON backup to move devices; see the privacy page.
Do I need an account?
No sign-up, paid API or subscription is required. Both languages use the same tools. English always opens at the root address.
SPINKIND / TOOLKIT
A little help for every step.
01
Gear speed
Calculate theoretical speed from cadence and wheel circumference.
Open tool02
Cadence target
Work back from a chosen speed to crank revolutions per minute.
Open tool03
Gear range
Compare the highest and lowest ratios for selected tooth counts.
Open tool04
Wheel rollout
Estimate circumference from measured outer wheel diameter.
Open tool