Grain Bill Calculator

About this calculator

A grain bill is the total malt weight a brewer needs to hit a target original gravity, calculated by working backward from the malt’s potential extract (points per pound per gallon, or a metric equivalent) and the brewhouse’s actual mash/lauter efficiency — the percentage of that theoretical sugar that actually ends up in the kettle, since real efficiency is always lower than the malt’s lab-rated maximum.

Homebrewers and small craft brewers calculate grain bills when designing a new recipe or scaling an existing one to a different batch size, because guessing at malt quantity either under-shoots the target gravity (leaving a thin, low-alcohol beer) or overshoots it — and because every brewhouse has different efficiency depending on mash tun design, crush quality and process, a recipe copied from elsewhere rarely hits the same gravity without recalculating for your own system’s efficiency.

This calculator takes your target gravity, batch size and brewhouse efficiency and returns the malt weight needed to reach that gravity.