VEX Gear Ratio Calculator

Advanced Calculator

Stage 1 Driver Teeth

Stage 1 Driven Teeth

Stage 2 Driver Teeth

Stage 2 Driven Teeth

Stage 3 Driver Teeth

Stage 3 Driven Teeth

Motor Speed RPM

Motor Torque N·m

Motor Count

Efficiency Percent

Wheel Diameter cm

Expected Load Torque N·m

Travel Distance m

Example Data Table

Mechanism	Driver Teeth	Driven Teeth	Overall Ratio	Typical Use
Fast wheel drive	36	12	1:3 overdrive	Higher speed with lower torque
Balanced drivetrain	24	24	1:1 direct drive	Simple speed and torque transfer
Robot arm	12	60	5:1 reduction	Higher torque for lifting
Compound lift	12 then 12	60 then 36	15:1 reduction	Strong motion with slower output

Formula Used

The stage ratio is found by dividing driven gear teeth by driver gear teeth.

Stage ratio = Driven teeth ÷ Driver teeth

The overall ratio is the product of all active stage ratios.

Overall ratio = Stage 1 × Stage 2 × Stage 3

Output speed falls when the ratio is above one. It rises when the ratio is below one.

Output RPM = Motor RPM ÷ Overall ratio

Output torque uses motor torque, motor count, ratio, and efficiency.

Output torque = Motor torque × Motor count × Overall ratio × Efficiency

Wheel speed uses wheel circumference and output RPM.

Linear speed = Output RPM × Wheel circumference ÷ 60

How to Use This Calculator

Enter the gear attached to the motor shaft as the driver gear.
Enter the gear receiving motion as the driven gear.
Add second and third stages only when using compound gearing.
Enter motor RPM, torque, motor count, and efficiency.
Add wheel diameter when checking drivetrain speed.
Enter expected load torque to review the torque margin.
Press the calculate button to show results below the header.
Use CSV or PDF download buttons to save the output.

VEX Gear Ratio Planning

A VEX drivetrain or arm feels right when speed and torque match the job. A gear ratio calculator helps you test that balance before building. It compares driver teeth and driven teeth for each stage. It also estimates output speed, output torque, wheel speed, and travel time. These values make design choices easier.

Why Gear Ratio Matters

Every gear pair trades speed for force. A larger driven gear creates reduction. The output turns slower, but torque increases. A smaller driven gear creates overdrive. The output turns faster, but torque drops. Robots need both ideas. Drivetrains often need speed. Lifts, claws, and conveyors often need extra torque. Compound gearing lets you stack stages without using huge gears.

Engineering Use

This tool supports single and compound trains. Enter the motor gear as the driver. Enter the gear receiving motion as the driven gear. Add more stages when shafts carry motion onward. The calculator multiplies stage ratios to get the final ratio. It then applies motor speed, motor torque, motor count, and efficiency. The wheel section converts output rotation into linear travel. That helps compare a fast chassis against a strong chassis.

Design Tips

Start with a realistic motor speed. Free speed is useful for comparison, but loaded speed is lower. Use efficiency to account for friction, shaft flex, and gear mesh losses. A value between seventy and ninety percent is often more realistic than perfect efficiency. Check the torque margin against expected load. A margin above one means the mechanism can move that load in theory. A higher margin is safer for acceleration and impacts.

Common VEX Builds

Use reduction for arms, elevators, and intakes that lift game objects. Use overdrive for light rollers or fast wheels. For drivetrains, test traction first. Extra speed is wasted when wheels skid during matches.

Practical Checks

Always consider gear spacing and support. Long shafts can twist. Unsupported gears can slip. Small gears can wear under heavy load. Also check whether the final direction matters. An odd number of external meshes reverses output rotation. An even number keeps direction the same. After calculating, build a small test. Measure real speed and current draw. Then adjust tooth counts until the robot behaves well.

FAQs

What is a VEX gear ratio?

It is the relationship between driver gear teeth and driven gear teeth. It shows how speed and torque change through a gear train.

What does reduction mean?

Reduction means the driven side turns slower than the motor side. It increases torque and is useful for arms, lifts, and heavy mechanisms.

What does overdrive mean?

Overdrive means the output turns faster than the input. It can increase drivetrain speed, but it lowers available torque.

Can this calculator handle compound gears?

Yes. Use stage two and stage three fields when power moves through multiple gear pairs on connected shafts.

Why include efficiency?

Real gear trains lose power from friction, alignment, shaft flex, and bearing drag. Efficiency makes the estimate more practical.

How is wheel speed calculated?

The calculator multiplies output RPM by wheel circumference. It then converts that rotation into linear meters per second.

What torque margin should I target?

A margin above one means the mechanism can move the load in theory. Higher values are better for acceleration and impacts.

Should I use free speed for motor RPM?

Free speed is useful for comparison. For better predictions, enter a lower loaded speed based on testing or motor data.