How to use this calculator
- Enter pedal force. Use the driver force at the pedal pad.
- Enter pedal ratio. Add the mechanical pedal leverage ratio.
- Set assist and bore. Set assist multiplier and master cylinder bore.
- Use pressure downstream. Carry line pressure into brake torque or caliper sizing.
How it works
The master cylinder converts pushrod force into hydraulic pressure. The calculator uses master force = pedal force x pedal ratio x assist and pressure = master force / master cylinder area.
Use this pressure in the brake torque calculator to estimate caliper clamp force and wheel braking torque.
Worked example
Verified against the live calculator
A 100 lbf pedal force, 6:1 pedal ratio, no assist and 1.0 in master bore gives about 760 psi of line pressure before real-system losses and travel effects.
Frequently asked questions
How do you calculate brake line pressure?
Multiply pedal force by pedal ratio and assist multiplier, then divide by master cylinder piston area.
What is pedal ratio?
Pedal ratio is the mechanical leverage from the pedal pad to the master cylinder pushrod.
What assist multiplier should I use?
Use 1 for manual brakes. For boosted systems, use measured or manufacturer data if available; booster assist is not constant over all conditions.
Does this include brake bias?
No. It calculates pressure in one hydraulic circuit before proportioning, balance-bar or ABS effects.
Method & assumptions
- Assist multiplier is treated as constant; real boosters have nonlinear behavior.
- Does not check pedal travel, master volume, caliper piston volume, brake bias, ABS, fluid temperature or flex.