How to use the calculator
The short version
The calculator compares two drivetrains side by side: your current setup on the left, a proposed setup you're considering on the right. Fill in both cards, and every result on the page — speed, climbing grade, gear range, jump size — updates instantly. You don't need to press a "calculate" button; there isn't one, because there's nothing to submit. Just edit the fields and watch the numbers change.
Just comparing two cassettes?
If your question is "should I run an 11-32t or an 11-34t," you don't need to touch most of the form. Leave the chainring and wheel size the same in both cards — they're already set to match by default — and only edit the two cassette text boxes, one per card. Every result you see (speed, climbing grade, jump %) will then reflect the cassette difference alone, with nothing else changing underneath it.
The most direct answer to "what actually changes" for a cassette-only comparison is the Jump % column in the comparison table, and the Biggest jump line in the blue key-differences bar above it — that tells you not just how much your climbing gear or range changes, but where the biggest step in cadence happens as you shift.
Setting up each side
- Chainrings — choose 1x, 2x, or 3x, then pick the tooth count for each ring. For 2x/3x, list the largest ring first.
- Wheel size — pick your wheel and tire combination from the dropdown. This affects speed, gear inches, and development, so keep it accurate.
- Cassette — type your sprocket sizes separated by commas, smallest to largest (e.g.
11, 13, 15, 17, 19, 21, 24, 28). This is the field you'll edit most often.
Rider settings (top strip)
Cadence, power output, rider + bike weight, and crank arm length all feed the climbing-grade estimate and the speed numbers. These apply to both drivetrains equally, so they don't change which setup wins — they just calibrate the numbers to feel realistic for how you actually ride. If the grade numbers look too high or too low compared to what you experience on real climbs, adjust the power slider until they match.
Reading the results
From top to bottom, the page gives you the same comparison at increasing levels of detail:
- Verdict card — a plain-English summary: what you gain, what you lose, and an overall read on the tradeoff.
- Key differences bar (blue) — the headline numbers at a glance: top speed, sustained grade, gear range, easiest gear speed, gear count, and biggest jump.
- Comparison table — every gear, side by side, with speed, climbing grade, and jump % color-coded (green/orange/red) for both setups.
- Chart — the same data plotted across all gears, toggle between speed and climbing grade.
- Full data table — gear ratio, gear inches, development, and gain ratio for every combination, for anyone who wants the raw numbers.
Rows with reduced opacity in the tables are technically possible but flagged as cross-chained (severe chain angle) — hidden from the main comparison by default, visible via the "Show all combinations" toggle if you want the complete picture.
Sharing a comparison
The Share your results button copies a link that encodes everything you've entered — both drivetrains, wheel sizes, rider settings, all of it. Anyone who opens the link sees the exact same comparison you're looking at, no re-entering data required. Useful for posting a comparison somewhere (like a forum thread) or asking someone else's opinion on a setup.
Starting over
Reset to defaults clears both cards back to the example comparison. The Imperial / Metric toggle switches units everywhere on the page at once — no need to re-enter anything.