Bike Gear Ratio Calculator | Road Bike Gear Chart, Cadence & Speed, Track Skid Patches, Tire Circumference, Chain Links
The Bike Gear Ratio Calculator is a free tool for comparing the gearing of road bikes, cross bikes, gravel bikes, MTBs, and track bikes with numbers. Enter the front gears (chainrings such as 50-34), rear gears (cassettes such as 11-34), the tire (700×25C, 28C, etc.), and cadence, and it lists the gear ratio, development (distance per pedal revolution), speed, gear inches, and gain ratio for every combination, along with the lowest and highest gears, gear range, rear step size (%), and cross-chain combinations. You can also see a table of gears that let you hold a target speed (such as 30km/h) at 80-95rpm, compare setups when swapping cranks or cassettes (compact ↔ semi-compact, 11-30 ↔ 11-34, etc.), find skid patch counts (one foot / both feet) and a quick-reference chart for track and fixed-gear bikes, get the tire circumference for bike computers from ETRTO with a roll-out measurement, and calculate chain link counts (derailleur and single-speed).
Gear ratio and speed table
Enter the front and rear tooth counts, tire, and cadence to list the gear ratio, development, and speed for every combination.
2 sprockets: 50-34T. Rear gears (sprockets / cassette)
12 sprockets: 11-12-13-14-15-17-19-21-24-27-30-34T. For two rings enter "50-34"; for a single enter "42"
Cadence (pedal revolutions per minute)
Value to show in the table
Lowest gear
34×34
Highest gear
50×11
Gear range
455%
Speed table (km/h)
Rows are the rear tooth count and columns are the front tooth count. Tire 700×28C (circumference 2,130mm), cadence 90rpm.
| Rear\Front | 50T | 34T | Step |
|---|---|---|---|
| 11T | 52.3 | 35.6 | — |
| 12T | 47.9 | 32.6 | 9.1% |
| 13T | 44.2 | 30.1 | 8.3% |
| 14T | 41.1 | 27.9 | 7.7% |
| 15T | 38.3 | 26.1 | 7.1% |
| 17T | 33.8 | 23.0 | 13.3% |
| 19T | 30.3 | 20.6 | 11.8% |
| 21T | 27.4 | 18.6 | 10.5% |
| 24T | 24.0 | 16.3 | 14.3% |
| 27T | 21.3 | 14.5 | 12.5% |
| 30T | 19.2 | 13.0 | 11.1% |
| 34T | 16.9 | 11.5 | 13.3% |
Gray strikethrough marks cross-chain combinations (outer ring × the two largest cogs, inner ring × the two smallest cogs). "Step" is the change from the next smaller cog; above 10% your cadence changes a lot when you shift. The front shift is a 47% step.
Gear layout (speed)
Speeds at 90rpm, lined up for each front ring. Wide gaps between dots mean big shift steps, and dots that overlap between rows are gears of the same weight.
All calculations run in your browser, and the numbers you enter are never sent to a server. Settings are saved in this browser.
ABOUT
About Bike Gear Ratio Calculator | Road Bike Gear Chart, Cadence & Speed, Track Skid Patches, Tire Circumference, Chain Links
The Bike Gear Ratio Calculator is a tool for comparing the gearing of road bikes, cross bikes, gravel bikes, MTBs, and track bikes with numbers. Enter the tooth counts of the front gears (chainrings) and rear gears (sprockets / cassette), the tire, and cadence, and it makes a table of gear ratio, development (distance per pedal revolution), speed, gear inches, and gain ratio for every combination, showing the lowest and highest gears, gear range, rear step size (%), and cross-chain combinations. With 50-34 × 11-34 and 700×28C, the lowest gear 34×34 gives 11.5km/h at 90rpm and the highest gear 50×11 gives 52.3km/h. It also calculates a table of gears that hold a target speed at 80-95rpm, a comparison when swapping cranks or sprockets, track and fixed-gear skid patch counts, tire circumference for bike computers, and chain link counts.
How to use Bike Gear Ratio Calculator | Road Bike Gear Chart, Cadence & Speed, Track Skid Patches, Tire Circumference, Chain Links
- 1On the "Gear ratio table" tab, choose the front gears (such as 50-34) and rear gears (such as 11-34) from the presets, or enter the tooth counts separated by "-"
- 2Choose the tire (700×25C, 28C, etc.) and the cadence (such as 90rpm)
- 3Choose the value to show in the table from speed, development, gear ratio, gear inches, and gain ratio, then check the lowest and highest gears, the rear step size, and cross-chain combinations
- 4On the "Cadence and speed" tab, find the gears that let you spin at 80-95rpm at the speed you want to cruise (such as 30km/h)
- 5Before changing a crankset or cassette, line up your current setup (A) and the setup you want (B) on the "Compare two setups" tab to see how much lighter the lowest gear becomes in %
- 6Use the "Track bike skid patches" tab for track bikes, the "Tire circumference" tab for bike computer settings, and the "Chain length" tab when replacing a chain
Great for
- List the gear ratio and the speed at 90rpm for every gear combination on a road bike
- Compare how much lighter climbing is with a compact crankset (50-34) versus a semi-compact (52-36)
- Find out how many percent lighter the lowest gear becomes when changing a cassette from 11-30 to 11-34
- Find which gears let you spin at about 90rpm when cruising at 30km/h
- Check the skid patch count (one foot / both feet) when choosing the gear ratio of a track or fixed-gear bike
- Find the tire circumference (700×25C, 28C, etc.) to enter into a cycling computer
- Calculate how many links to cut a chain to when replacing it (derailleur and single-speed)
- Compare gear weight with bikes that have different wheel sizes or crank lengths using gear inches and gain ratio
Good to know
- Calculations use: gear ratio = front teeth ÷ rear teeth; development (m) = gear ratio × tire circumference; speed (km/h) = development × cadence × 60 ÷ 1000; gear inches = gear ratio × tire diameter (inches); gain ratio = tire radius ÷ crank length × gear ratio.
- Tire circumference is a calculated value from the ETRTO numbers as π × (bead seat diameter + tire width × 2). Even with the same marking, it varies by about ±1% depending on the manufacturer, rim inner width, air pressure, and body weight, so enter a roll-out (measured) value if you want it accurate.
- Cross-chain is defined, when there are two or more front rings, as "outer ring × the two largest rear cogs" and "inner ring × the two smallest rear cogs". These are combinations where the chain runs at an angle, which can cause noise and faster wear.
- "Number of usable gears" counts the gears, excluding cross-chain, whose gear ratio differs from other gears by 3% or more.
- For skid patches, the denominator (rear side) after reducing the front and rear tooth counts is the one-foot count, and if the numerator (front side) is odd, it doubles with both feet.
- For chain length (derailleur), both the formula that rounds up "2 × chainstay + largest front ÷ 4 + largest rear ÷ 4 + 1" (inches) and the method of wrapping the chain around the big-big combination and adding 2 links are shown. For derailleurs and full-suspension MTBs, follow the manufacturer's instructions first.
- The tooth counts of the preset cassettes are examples of common configurations. If they differ from the markings on your product, enter the tooth counts directly.
- All calculations run in your browser, and the numbers you enter are never sent to a server.
Questions this tool answers
Use Bike Gear Ratio Calculator | Road Bike Gear Chart, Cadence & Speed, Track Skid Patches, Tire Circumference, Chain Links for searches like these:
- I want to calculate the gear ratio of a road bike
- I want to calculate speed from gear ratio and cadence
- I want to compare the gear ratios of compact and semi-compact cranksets
- I want to know the difference between 11-30 and 11-34 cassettes
- I want to calculate the gear ratio and skid patch count of a track bike
- I want to set the tire circumference of 700×25C or 700×28C on my cycling computer
- I want to calculate a bike chain's length (number of links)
- I want to calculate gear inches and gain ratio
FAQ
- How do you calculate a bike's gear ratio?
- It is the number of teeth on the front gear (chainring) divided by the number of teeth on the rear gear (sprocket). With 50T × 17T the gear ratio is 2.94, meaning the rear wheel turns 2.94 times per pedal revolution. Multiply that by the tire circumference (about 2,130mm for 700×28C) to get a development of 6.26m, and at a cadence of 90rpm that is 6.26m × 90 × 60 ÷ 1000 = about 33.8km/h.
- How fast do you go at a cadence of 90?
- It depends on the gear and the tire. With 700×28C, 50×17 gives about 33.8km/h, 50×15 about 38.3km/h, the highest gear 50×11 about 52.3km/h, and the lowest gear 34×34 about 11.5km/h. To reach 30km/h you need a cadence of about 80rpm with 50×17 and about 70rpm with 50×15.
- How different is climbing between compact and semi-compact?
- Comparing the lowest gears, the low of 50-34 × 11-34 is 34×34 (gear ratio 1.00), and the low of 52-36 × 11-30 is 36×30 (gear ratio 1.20), so the semi-compact is 20% heavier. At 90rpm with 700×28C, that is 11.5km/h versus 13.8km/h. Use the "Compare two setups" tab to compare your own setups.
- How much lighter does it get if I change the cassette from 11-30 to 11-34?
- With the 34T inner ring, the low goes from 34×30 (1.13) to 34×34 (1.00), about 12% lighter. In exchange the rear steps get larger, and with 11-34 there are several steps of around 13%, so you may feel there is no gear that is just right on flat roads.
- What is a skid patch, and how is it calculated?
- On a fixed gear (track bike), it is the number of spots where the tire rubs against the ground when you skid to a stop. Reduce the front and rear tooth counts; the denominator (rear side) is the count when skidding with one foot, and if the numerator (front side) is odd, it is double that with both feet. 48×17 cannot be reduced, so it is 17 spots for one foot or both; 46×16 is 23/8, so 8 spots for one foot and 16 for both; 48×16 is 3/1, so 1 spot for one foot and 2 for both, and only the same places wear out.
- What is the tire circumference of 700×25C or 700×28C in mm?
- As calculated from ETRTO, 700×23C (23-622) is about 2,099mm, 700×25C (25-622) about 2,111mm, 700×28C (28-622) about 2,130mm, and 700×32C (32-622) about 2,155mm. The real circumference varies by about ±1% with the tire brand and air pressure, so for accurate cycling computer distance, roll the tire a few revolutions and measure it.
- What is the difference between gear inches and gain ratio?
- Gear inches is gear ratio × tire diameter (inches), and lets you compare gear weight between bikes with different tire sizes. Gain ratio also includes the crank length (tire radius ÷ crank length × gear ratio), and is the ratio of the distance the bike travels to the distance the pedals move. With 50×17 and 700×28C, gear inches is 78.5, and gain ratio is 5.87 with a 170mm crank and 5.78 with a 172.5mm crank.
- How many links should a road bike chain have?
- It is determined by the chainstay length and the largest front and rear gears. With a 410mm chainstay, 50-34, and 11-34, the formula "2 × chainstay (inches) + front ÷ 4 + rear ÷ 4 + 1" rounded up gives 110 links, and the method of wrapping around big-big and adding 2 links also gives 110 links. New chains come with 116-126 links, so cut it to the calculated number of links.
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