Pulley Torque Calculator

A pulley can move a load with ease. But torque tells you how much twist it can make.

Our Pulley Torque Calculator helps you find pulley torque fast. You can use it for belt drives, force loads, and motor power.

The tool uses simple input values. It then gives the torque in N·m. It also shows other common torque units.

You can use this tool for machine design and motor work. It can also help with belt drive checks and pulley setup using a Motor Torque Calculator.

Whether you need a torque calculator for pulley work or a pulley calculator torque tool, this page keeps it simple.

Pulley Torque Formula

The main pulley torque formula for a belt drive is:

T = (T₁ − T₂) × r

Here:

T = pulley torque in N·m

T₁ = tight-side belt force in N

T₂ = slack-side belt force in N

r = pulley radius in meters

Think of a belt like two people pulling a wheel. One side pulls hard. The other side pulls less. The gap between these two pulls creates torque.

So, first find the net belt force:

F = T₁ − T₂

Then find torque:

T = F × r

If you know the pulley diameter, use:

r = D ÷ 2

So the full formula becomes:

T = (T₁ − T₂) × (D ÷ 2)

Other Pulley Torque Formulas

The calculator also supports two other methods.

For a force at an angle:

T = F × r × sin(θ)

Here, θ is the angle between force and the lever arm.

For motor power and speed:

T = P ÷ ω

Here, P is power in watts. The symbol ω means angular speed in rad/s.

If you enter RPM, the tool uses:

ω = (2 × π × RPM) ÷ 60

This method can help when you know motor power and shaft speed.

How to Use Online Pulley Torque Calculator

Using the online pulley torque calculator is easy. Just follow these steps.

1. Choose a calculation mode. Pick belt tension, force and lever arm, or power and speed.
2. Enter your values. Add the belt force, radius, diameter, power, or speed as needed.
3. Pick the right units. You can use N, kN, lbf, or kgf for force. Length can use m, cm, mm, in, or ft.
4. Click the calculate button. The tool will convert the values and run the right formula.
5. Read your torque result. The result shows torque in N·m. You can also view kN·m, N·mm, ft·lb, in·lb, and kgf·m.

You don't need to do unit math by hand. The tool handles the unit changes for you.

Example Pulley Torque Calculation

Let's say a belt drive has these values:

T₁ = 800 N

T₂ = 300 N

Pulley diameter = 0.4 m

First, find the pulley radius:

r = 0.4 ÷ 2

r = 0.2 m

Now find the net belt force:

F = 800 − 300

F = 500 N

Now use the pulley torque formula:

T = 500 × 0.2

T = 100 N·m

So, the pulley torque is:

100 N·m

The calculator can also show this value in other units.

For example:

100 N·m = 0.1 kN·m

100 N·m = 100,000 N·mm

100 N·m ≈ 73.7562 ft·lb

100 N·m ≈ 885.0746 in·lb

This example shows how the pulley torque calculator finds the result. The key step is the difference between tight-side and slack-side belt force.

Pulley Torque, RPM, and Pulley Size

Torque and speed often work together. This matters in motor and belt drive systems.

A motor pulley size calculator can help compare pulley sizes. A pulley size RPM calculator can help find speed changes.

For two pulleys, the ideal belt speed stays the same. This gives the basic relation:

D₁ × RPM₁ = D₂ × RPM₂

So:

RPM₂ = (D₁ × RPM₁) ÷ D₂

This is useful for a pulley to pulley RPM calculator.

A larger driven pulley runs slower. A smaller driven pulley runs faster. It's a simple trade-off.

The same idea helps when you need to compare pulley speed and torque. In an ideal drive, a speed drop can give a torque gain. Real systems may lose some power due to friction and other losses.

Final Verdict

The Pulley Torque Calculator makes torque math quick and clear. It supports belt tension, force and angle, and motor power methods.

For belt drives, the main formula is:

T = (T₁ − T₂) × r

For force and angle, use:

T = F × r × sin(θ)

For power and speed, use:

T = P ÷ ω

The tool also handles unit conversion. So, you can focus on the result instead of doing long math by hand.

If you're checking a belt drive, motor setup, or pulley system, this calculator can save time and reduce errors.

FAQs

What is a pulley torque calculator?

A pulley torque calculator finds the torque produced or carried by a pulley. It can use belt tension, force, radius, power, or speed.

What is the main pulley torque formula?

For a belt drive, the main formula is T = (T₁ − T₂) × r.

Can I use pulley diameter instead of radius?

Yes. The calculator can accept pulley diameter. It first finds the radius with r = D ÷ 2.

What is the difference between tight-side and slack-side tension?

The tight side has higher belt tension. The slack side has lower tension. Their difference creates the net force that drives the pulley.

Can I calculate pulley torque from motor power?

Yes. If you know power and angular speed, use T = P ÷ ω.

Can this tool calculate pulley RPM?

The power mode uses RPM to find torque. The pulley speed relation can also help compare two pulleys:

RPM₂ = (D₁ × RPM₁) ÷ D₂

What units does the calculator use?

The main result is in N·m. It can also show kN·m, N·mm, ft·lb, in·lb, and kgf·m.

Does pulley size affect torque?

Yes. For the same net belt force, a larger pulley radius gives more torque. However, pulley size also affects belt speed and system ratio.