Calculation Results
Calculated estimations for your inputs:
RPM vs Speed Reference Table
| Engine RPM | Speed |
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A gear ratio calculator computes velocity ratios, speed reductions, torque multipliers, and output shaft RPMs for spur and helical gear trains. Essential for automotive mechanics, bicycle engineers, and industrial drive designer logs.
How to Calculate Gear Ratios
Gearing layout multiplies input forces while dividing rotational velocities. Sizing gear teeth and tooth count must comply with AGMA engineering guidelines to ensure durable service [1].
Gear Speed Formulas
- Gear Ratio: Gear Ratio = (Driven Teeth) ÷ (Drive Teeth)
- Output Speed (RPM): Output RPM = (Input RPM) ÷ (Gear Ratio)
Sources & References
- AGMA Standard 908-B89: Geometry Factors for Determining the Pitting Resistance of Spur Gears Source Link
- ISO 6336: Calculation of load capacity of spur and helical gears Source Link
- SAE J1282: Automotive Gear Design Guidelines Source Link
- ANSI/AGMA 2001-D04: Fundamental Rating Factors for Spur and Helical Gear Teeth Source Link
- Machinery's Handbook, 31st Edition: Gear geometry and ratios Source Link
- DIN 3990: Calculation of load capacity of cylindrical gears Source Link
- JIS B 1702: Cylindrical gears - Accuracy grades Source Link
- SME Manufacturing Engineers Handbook: Gear trains Source Link
- AGMA 913-A98: Method for Predicting the Strength of Spur Gear Teeth Source Link
- ISO 53: Cylindrical gears for general and heavy engineering Source Link
Frequently Asked Questions (FAQ)
How is gear ratio calculated?
Gear ratio is calculated by dividing the number of teeth on the driven gear by the number of teeth on the drive (pinion) gear: Gear Ratio = Driven Teeth / Drive Teeth.
What is a speed reduction ratio?
A speed reduction ratio multiplies output torque while reducing speed. A 3:1 gear ratio means the input shaft turns three times for every single rotation of the output shaft.
How does gear ratio affect torque?
Output torque is directly proportional to gear ratio (ignoring friction losses). A 4:1 gear ratio multiplies input torque by 4, allowing smaller motors to turn heavy loads.
What is gear backlash?
Backlash is the clearance gap between mating gear teeth, designed to prevent binding, allow lubrication, and account for thermal expansion under load.
What is a pinion gear?
The pinion is the smaller gear in a mating pair, usually mounted on the drive shaft (input) to initiate rotational speed transfers.
How do you calculate compound gear ratio?
For compound gear trains, calculate the individual ratio of each gear pair, then multiply them together: Total Ratio = Ratio 1 × Ratio 2 × Ratio 3.
How does tire diameter affect final drive speed?
In automotive drivetrains, overall speed depends on transmission ratio, final drive ratio, and tire diameter. Larger tires cover more ground per rotation, increasing top speed but reducing acceleration torque.
What is the gear pitch circle?
The pitch circle is the imaginary circle where the mating teeth of two gears contact, used to calculate nominal diameters and velocity ratios.
Why do gears have helical cut teeth?
Helical gears feature angled teeth that engage gradually, reducing noise and vibrations compared to straight-cut spur gears, making them standard in automotive gearboxes.
How do you calculate speed from gear ratio and RPM?
Output RPM is equal to Input RPM divided by the Gear Ratio. Vehicle speed is then calculated using output RPM, final drive, and tire circumference.