⚙️ Gear Ratio Calculator
Calculate gear ratio, output RPM, torque multiplication, and mechanical advantage for any gear system
| Gear Ratio | Input 1750 RPM | Input 3450 RPM | Torque Multiplier | Application |
|---|---|---|---|---|
| 1:1 | 1750 RPM | 3450 RPM | 1.0x | Direct Drive |
| 2:1 | 875 RPM | 1725 RPM | 2.0x | Moderate Reduction |
| 4:1 | 438 RPM | 863 RPM | 4.0x | General Machinery |
| 5:1 | 350 RPM | 690 RPM | 5.0x | Conveyor / Feed |
| 10:1 | 175 RPM | 345 RPM | 10.0x | Heavy Equipment |
| 20:1 | 88 RPM | 173 RPM | 20.0x | Worm / Actuator |
| 50:1 | 35 RPM | 69 RPM | 50.0x | Wind Turbine |
| 100:1 | 18 RPM | 35 RPM | 100.0x | Indexing Table |
| Gear Type | Efficiency | Max Ratio (Single) | Backlash | Noise Level | Best Use |
|---|---|---|---|---|---|
| Spur Gear | 97-99% | 10:1 | Low | Moderate | Parallel shafts |
| Helical Gear | 96-98% | 10:1 | Very Low | Low | High-speed drives |
| Bevel Gear | 95-97% | 6:1 | Low | Moderate | Right-angle drives |
| Worm Gear | 50-90% | 100:1 | Moderate | Low | High reduction |
| Planetary Gear | 97-99% | 12:1 | Very Low | Low | Compact high-torque |
| Chain Drive | 93-98% | 8:1 | Low | High | High-load transport |
| Belt Drive (Flat) | 95-98% | 6:1 | None | Very Low | Light-duty smooth |
| Belt Drive (V) | 93-97% | 7:1 | None | Low | Motor to pump/fan |
| Application | Driver Teeth / Dia | Driven Teeth / Dia | Ratio | Input RPM | Output RPM |
|---|---|---|---|---|---|
| Bicycle (Low) | 28T (chain) | 34T | 0.82:1 | 80 RPM | ~65 RPM |
| Bicycle (High) | 50T (chain) | 11T | 4.55:1 | 90 RPM | ~409 RPM |
| Auto Trans 1st | — | — | 3.4-4.2:1 | 800 RPM | ~225 RPM |
| Auto Trans 4th | — | — | 0.7-1.0:1 | 2000 RPM | ~2000 RPM |
| Drill Press | 3 in pulley | 6 in pulley | 2:1 | 1750 RPM | 875 RPM |
| Lathe Headstock | 20T | 80T | 4:1 | 1750 RPM | 438 RPM |
| Wind Turbine | — | — | 50-100:1 | 20 RPM | 1000-2000 RPM |
| Robot Joint | 1 (worm) | 100T | 100:1 | 1200 RPM | 12 RPM |
At the heart of everything, the report of gears simply is a math relation between two gears, that mesh together. One writes it as relation between input and output (so if you see 3:1 that points), that the input shaft turns happen thrice for every one rotation of the output shaft. But here the main spot: one Gear alone do not fit anything useful do.
You need two gears, that work together as partners, to hand over torque, speed, force or spin direction.
How Gear Ratios Work
Speed and torque has this reverse relation, what is important to understand. When the speed rises, the torque sinks. And the other way, when torque grows, the speed drops.
Think about gears like twisting levers. If you alter the report, the arm of the lever becomes longer or shorter. Like this the system can push out huge force from almost any rotation or turn, even from little input.
Find the report are not difficult. One can divide the edge of the output Gear by that of the input Gear. But really, the simplest way?
Simply count the teeth. When two gears mesh, divide the number of teeth of one Gear by taht of the other gives the report. Assume, that you have 100 tooth Gear combined with 40 tooth.
One full turn of the big Gear passes 100 teeth past the little, what matches around 2.5 rotations. That results in 1:2.5 report.
Reports one says as something against one. In a real car, the first Gear could be around 3.5:1, quite a lot strong. The highest Gear?
More near 0.7:1, where the Gear of the engine is actually bigger then that of the wheels. Also there is the differential, that goes to the wheels and add his own permanent report, around 3.5:1.
Engines work best in a certain range of RPM, not through the whole range. The reports of gears act as big controls, they turn the engine speed up or down, while they control, how much torque reaches the rolling wheels. Transmissions serve to keep the engine humming in that perfect zone, while you speed up or brake.
Higher report, for instance 4.11, do the speed up of the car slower, because the engine must twist more quickly and create bigger power at the wheels. Lower reports? They need fewer engine turns for one wheel turn, what is more saving forthe fuel tank.
Combined systems become really complex. If you tie two pairs of gears, their separate reports multiply together. Take first pair in 7:21 and second in 9:30…
Multiply them and you get 63:630, what simplifies to 1:10. The reports in a set of gears can sit close together, spread out a lot or combine both ways. Narrow spaces in the bottom gears help for hard speed up, while bigger differences in the upper give better ability for top speed.
