Calculator to find out if a pipe organ has drifted from the reference pitch.
1. Check for drift — fill in all four fields. The calculator corrects your measured pitch back to the reference temperature and reports the deviation in cents.
2. Find the target pitch — fill in the reference pitch, the reference temperature and the measured temperature, and leave the measured pitch blank. The calculator reports the frequency the reference pitch corresponds to at the measured temperature — the pitch you should actually tune to right now — both in Hz and as a cent offset from the reference, for tuning devices that work in cents.
Example: an organ set to A 440 Hz at 70 °F (21.1 °C) needs to be tuned to about 446.0 Hz when the room is 84 °F (28.9 °C) — roughly 23 cents sharp.
The °C / °F toggle applies to both temperature fields and works the same way in either mode. Switching units converts the values already entered — it does not change the result.