Calculator
Headroom calculator: how much you can add before crossing a proof
Not 'what will the proof be' but 'how much can I pour before I cross my line.' The calculator solves for the volume directly.
4.4
OZ YOU CAN ADD BEFORE CROSSING 110
The formula
x = V x (T - P) / (p - T)
V is current volume, P current proof, p the incoming proof, T the target. 20 oz at 106.7, target 110, incoming 124.9 gives 4.4 oz. Derivation and edge cases.
Reading a strange answer
- No limit: the incoming proof is at or below the target, so it can never push you past it.
- Zero: the bottle is already past the target. The fix is water or a softer whiskey.
- Floor mode: if the incoming whiskey is below the current proof and you set a target below current, the calculator answers how much you can add before sinking below it.
The app that keeps these books for you
Thief & Blend tracks every pour, runs the proof math live, and remembers how much of the first pour survives. On the App Store for iPhone.
DOWNLOAD FOR iOS