Rates do not add up.

Balthazard combines impairment rates the way the formula actually works: each rate applies to what the ones before it left whole. Free, offline, and on iPhone and iPad.

App Store How it works

Three rates entered, with the combined result and the running total after each one — The combined rate, and the working behind it.

A rate being set on two wheels: whole percent and hundredths — Wheels, not a keyboard. Nothing outside 0 to 100 can be entered.

The formula

Two impairments of 25.5% and 12% do not make 37.5%. The second applies to the 74.5% left whole by the first, so the total is 34.44%:

total = 0
for each rate r:  total = total + r x (100 - total) / 100

The order of the rates does not change the answer, and the total approaches 100% without ever reaching it. In Turkish forensic medicine this is how several separate impairments are reduced to one figure — birlesik maluliyet orani.

What it does

As many rates as you need
Each set on a wheel, so there is no invalid input and no decimal separator to guess at
The running total after each rate, shown on request
English, Turkish, German, French, Spanish and Italian
No account, no network, no analytics, no adverts

First published in 2013 and rebuilt from scratch in 2026.