The LebelBicycles bike gear ratio calculator shows you exactly how your bike's gears perform. Enter your chainrings, cassette, and wheel size, or pick a drivetrain preset. You get a colour-coded grid of every gear. Each one shows its ratio, gear inches, development, gain ratio, and speed. Now you can compare setups at a glance and pick the right one.
Bike Gear Ratio Calculator
Gear inches, development, gain ratio & speed — all at once.
Single-speed
Swipe the table sideways to see every gear.
50T × 17T
Enter at least one chainring and one cog to see your gears.
Speeds assume no slip and the cadence you set. Gear inches & development use your wheel’s inflated circumference — set a measured rollout for the most exact result.
How gear ratios work
Gear ratio = chainring teeth ÷ cog teeth. A 50T ring with a 17T cog is 50 ÷ 17 = 2.94 — the wheel turns 2.94 times per pedal stroke.
Gear inches = ratio × wheel diameter (inches). Development is how far you roll per stroke (circumference × ratio). Gain ratio (Sheldon Brown’s metric) factors in crank length, so it’s the fairest comparison across bikes. Speed = development × cadence: a bigger ratio or faster cadence means more speed.
How Do Bike Gear Ratios Work?
A bike gear ratio is the number of times the rear wheel turns for one full turn of the pedals. You find it by dividing the front chainring teeth by the rear cog teeth. A higher ratio runs faster but harder; a lower one spins easier to climb.
What Is a Bike Gear Ratio?
A bike gear ratio is the front chainring tooth count divided by the rear cog tooth count. A 50-tooth chainring with a 25-tooth cog gives a ratio of 2.0, so the rear wheel turns twice per turn of the cranks. The ratio is a pure unitless number, the quickest way to compare gears.
How Do You Calculate a Gear Ratio?
You calculate a gear ratio by dividing the chainring teeth by the cog teeth.
Gear ratio = chainring teeth ÷ cog teeth
A 46-tooth chainring with a 16-tooth cog gives 46 ÷ 16 = 2.875.
| Chainring × cog | Ratio | Feel |
|---|---|---|
| 34 × 32 | 1.06 | Very easy climbing |
| 50 × 25 | 2.00 | All-round |
| 50 × 17 | 2.94 | Fast cruising |
| 52 × 13 | 4.00 | Sprint |
| 50 × 11 | 4.55 | Top-end speed |
What Are Gear Inches?
Gear inches express a gear ratio as the wheel diameter a penny-farthing would need to deliver the same gear.
Gear inches = gear ratio × wheel diameter (inches)
A 50×17 ratio of 2.94 on a 700c wheel of about 26.4 inches gives roughly 77.6 gear inches. Numbers around 20 to 30 are climbing gears; above 100 are racing gears.
What Is Development or Rollout?
Development, also called rollout, is the distance in metres the bike travels in one full turn of the pedals.
Development = wheel circumference (m) × gear ratio
A 700c wheel with a 2.215-metre circumference in a 36×10 gear (ratio 3.6) rolls 2.215 × 3.6 = 7.97 metres per pedal stroke.
What Is a Gain Ratio?
A gain ratio is a gear measurement that includes crank length, so it reflects the mechanical advantage your legs feel. Cycling writer Sheldon Brown defined it as the distance the bike travels divided by the distance the pedals travel.
Gain ratio = (wheel radius ÷ crank length) × gear ratio
A 700c wheel with a 336 mm radius, a 170 mm crank, and a 50×17 ratio of 2.94 gives (336 ÷ 170) × 2.94, about 5.8. It is the fairest measure, since it alone counts crank length.
What Speed Does a Gear Ratio Give at a Set Cadence?
A gear ratio reaches a specific speed once you fix a cadence, your pedalling rate in revolutions per minute. Most riders cruise between 80 and 100 rpm.
Speed (km/h) = development (m) × cadence (rpm) × 60 ÷ 1000
A gear with 7.97 metres of development at 90 rpm produces 7.97 × 90 × 60 ÷ 1000 = 43.0 km/h, which is 26.7 mph. The same gear at 60 rpm drops to about 28.7 km/h. The bike pace and speed calculator turns a target speed into a finish time.
Other Gear Ratio Topics: Drivetrains, Wheel Size, and Climbing
These go beyond the core numbers above. Open the topic that fits your setup:
What is the difference between 1×, 2×, and 3× drivetrains?
The difference between 1×, 2×, and 3× drivetrains is the number of front chainrings, which sets your range. The three layouts are described below.
- 1× (single chainring). One chainring and a wide cassette, with no front derailleur. It is standard on mountain and gravel bikes, where a 32-tooth ring with a 10–52 cassette covers most terrain.
- 2× (two chainrings). Two chainrings, such as 50/34, with a close-spaced cassette. It is the road default, with wide range and fine cadence steps.
- 3× (three chainrings). A third, smaller chainring adds the lowest gears, common on touring bikes.
More chainrings widen the range but overlap gears. The calculator above flags overlap and the jumps between gears.
How do gear ratios work on single-speed and fixed-gear bikes?
A single-speed or fixed-gear bike has one fixed ratio, so the chainring and cog are the whole gearing decision. A common track ratio is 46×16, giving 2.875, or about 75 gear inches. Lower ratios such as 44×18 favour climbs; higher ratios such as 48×15 favour flat speed.
Fixed-gear riders also track skid patches, where the rear tire meets the ground during a skid. The count equals the cog teeth divided by the greatest common divisor of the chainring and cog. A 46×16 gear has a divisor of 2, giving 16 ÷ 2 = 8 patches. Teeth counts with no common factor, such as 47×17, give the most.
How does wheel and tire size affect gear ratios?
Wheel and tire size do not change the gear ratio itself, but they change every distance-based and speed-based result. The table below shows the same 50×17 gear at three wheel sizes.
| Wheel size | Gear inches | Development |
|---|---|---|
| 26″ MTB | ~75.9 | ~6.10 m |
| 700c road | ~77.6 | ~6.19 m |
| 29″ MTB | ~84.8 | ~6.76 m |
How do you choose a gear ratio for climbing?
You choose a climbing gear by setting your lowest gear so it spins a comfortable cadence up your steepest hill. A good benchmark is a gear at or below 1.0, under about 30 gear inches on most wheels, holding cadence above 60 rpm. A 34×34 gives a 1.0 ratio, a common road climbing gear, while a 1× mountain setup of 32×52 drops to about 0.62 for very steep terrain.
How Do You Use This Gear Ratio Calculator?
This calculator turns your setup into a table of gear ratio, gear inches, development, gain ratio, and speed. Enter it below.
- Pick a drivetrain preset. Road, Gravel, MTB 1×, BMX, Single-speed, or Fixed, then adjust any field.
- Enter chainrings and cassette. One to three chainring sizes and a cassette preset or your own cogs.
- Set wheel, tire, and crank. Your ISO wheel and tire size, plus crank length for the gain ratio.
- Set cadence. A pedalling rate, in km/h or mph.
The grid shows every combination as a colour-coded heatmap, each cell giving gear inches, development, gain ratio, and speed, plus a skid-patch count in single-speed and fixed-gear modes.
