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Brake pedal ratio and line pressure calculator

Pedal ratio, the force reaching the master cylinder, and the line pressure it makes. Handy when swapping to manual brakes, changing master cylinders or building a custom pedal.

Enter your numbers
Pedal
1 for manual brakes. Power boosters vary; check the booster's rating.
Master cylinder

Line pressure

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Pedal ratio
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Force on the master cylinder
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Master cylinder piston area
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Manual and power ratios differ

Manual brakes generally use a higher pedal ratio, often around 6:1, while power brakes typically run about 4:1. Using a power-brake pedal without a booster makes the pedal hard.

The formulas

Pedal ratio = pivot-to-pad distance ÷ pivot-to-pushrod distance
Pushrod force = foot force × pedal ratio × booster multiplier
Line pressure (psi) = pushrod force ÷ master cylinder piston area

The pedal is a lever that multiplies your foot's force. A smaller master cylinder bore makes more pressure from the same force but moves less fluid, so the pedal travels farther. Bigger bores do the opposite.

Measure the pedal distances with the pedal at rest, from the pivot bolt center to the center of the pad and to the pushrod pin.

Frequently asked questions

Why does pedal ratio matter so much for brake feel?

Pedal ratio multiplies the force your foot applies before it ever reaches the master cylinder, so a low ratio can leave you pushing hard for modest line pressure, while too high a ratio can make the pedal feel overly touchy — it's a real tuning variable, not just a mounting detail.

Why do I need to account for a brake booster separately?

A vacuum or hydraulic booster adds its own force multiplication on top of the mechanical pedal ratio, so leaving it out of the calculation would significantly understate the actual force reaching the master cylinder on a boosted brake system.

What line pressure should I be targeting?

It depends heavily on your specific caliper and pad combination, but many performance brake systems are designed around roughly 1,000-1,200 psi at hard braking — check your caliper manufacturer's specs rather than assuming one universal target applies to every setup.

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