CalculatorsBicycle Gear Ratio Calculator
SRAM Force 1 40 gearing with SRAM Red XG-1290 10-33T
Standard 1x gravel setup providing a great balance of top speed and climbing ability. One-piece machined road cassette utilizing a 10T cog for higher top speed.
Easiest 1.21, hardest 4.00
The easiest gear (40 / 33) gives a ratio of 1.21, and the hardest (40 / 10) gives 4.00.
Endurance gearing: the bail-out is real, and the top end is still a fast road gear. The spread from 1.21 to 4.00 stays tighter, so cadence jumps are smaller and the bail-out is modest.
SRAM Force 1 is a 1x gravel ring (BCD 107, 11/12 -speed) on a 12-speed SRAM cassette with a XDR freehub. The chainring is listed as Gravel and the cassette as Road, so this is a mixed (mullet) build: confirm the derailleur cage and the chain before you assume it shifts.
Every chainring tooth against every cog
| Chainring | 10 | 11 | 12 | 13 | 14 | 15 | 17 | 19 | 21 | 24 | 28 | 33 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 40 | 4.00 Hardest | 3.63 | 3.33 | 3.07 | 2.85 | 2.66 | 2.35 | 2.10 | 1.90 | 1.66 | 1.42 | 1.21 Easiest |
Inputs
Results
- Gear ratio
- 4.00
How the number is made
Ratio = chainring ÷ cog. Published figures are truncated to two decimal places, so 36 ÷ 34 is shown as 1.05 and 52 ÷ 11 as 4.72. The live form uses the same truncation.
Ratio ignores wheel size. Gear inches and rollout add the tyre.
- Gear ratio. Truncated to two decimal places.
How pair pages are chosen
A chainring is paired with a cassette only when the cassette speed is in the chainring’s compatible-speed list. A track ring and a 12-speed cassette are not given a URL.
Related calculators
- Gear Inches and Roll-out Calculator
Same teeth, different development once the wheel size is in the sum.
- Cadence to Speed Calculator
Turns this ratio into km/h at the cadence you actually hold.
- Cassette Range Calculator
The percent range is the cassette alone, before a chainring is chosen.
Questions
What is a climbing ratio?
Around 1.0 or below (for example 36÷34 or 34÷51) lets you spin a steep grade. Above 1.5, the easiest gear is already hard work.
Why truncate to 1.05 instead of rounding to 1.06?
36÷34 is 1.0588. This site truncates to two decimals so every pair page quotes the same published figure.
Does the chainring brand change the ratio?
No. Teeth do. Brand, speeds and freehub decide whether the pair can be built.
Related gear
- Replacement cassette
Match the freehub (HG, Micro Spline, XD, XDR) before the tooth count.
$40–$400
- Matching chain
Speed count of the chain has to match the cassette, not just the chainring brand.
$20–$80