How do you calculate brewhouse efficiency?
Divide the sugar you got by the sugar the grain could have given you. Both sides are measured in gravity points × volume: the bill's potential is each fermentable's weight × its extract potential (37 PPG for pale malt, and so on — the same table the Expected OG calculator uses); what you got is the OG points × the volume that reached the fermenter.
Brewhouse efficiency = (OG points × volume into fermenter) ÷ Σ (weight × potential)
Eleven pounds of pale malt and one of crystal is 441 point-gallons of potential. Land 1.050 in 5.5 gallons and you kept 50 × 5.5 = 275 of them: 62%. Land 1.058 in the same 5.5 gallons and it's 72%. Land the original 1.050 but in 6.0 gallons and it's 68% — the volume you measure is worth as much as the gravity, which is why the efficiency you can't reproduce is usually a volume you didn't measure.
Mash efficiency vs brewhouse efficiency — which number goes where?
They're the same measurement taken at different points, and the difference between them is your kettle. Mash (or lauter) efficiency is measured pre-boil: how much of the potential made it out of the mash tun and into the kettle. Brewhouse efficiency is measured into the fermenter, after the trub and the kettle's deadspace have kept their share. Same sugar, less wort — so brewhouse is always lower, by exactly the fraction of wort you leave in the kettle. On the default profile a 72% brewhouse brew shows about 79% at pre-boil, and the 0.5 gal of kettle loss accounts for the 6.5-point gap. That is the whole ladder:
| Stage | What's measured | Efficiency name | Where it goes |
|---|---|---|---|
| Grain bill | Potential at 100% (441 pt·gal) | — | The denominator for everything |
| Kettle, pre-boil | Pre-boil gravity × cooled volume | Mash / lauter efficiency (~79%) | Calculators that ask for "wort collected"; Brewer's Friend's efficiency tool |
| Fermenter | OG × volume into fermenter | Brewhouse efficiency (72%) | Your equipment profile — Expected OG, Brew Day, recipe scaling |
Default US profile: 5.5 gal batch, 0.5 gal kettle loss, from this page's engine. Boil-off doesn't change efficiency — the same points end up in less water — but kettle loss does, because that wort never leaves.
Every calculator on this site that divides by "volume into the fermenter" wants the brewhouse number — that's Expected OG, Brew Day and the grain-for-target table. Type a mash efficiency into them and every prediction runs high by your kettle-loss share (typically 3–7 points of OG). This page reports both, labels both, and the save button stores the right one.
What's a normal brewhouse efficiency?
For homebrew systems, 65–80%, with 70–75% the fat middle. Coolers with a decent crush and a careful batch sparge run 70–78; fly spargers a little higher; BIAB anywhere from 65 to 80 depending on crush fineness and whether you squeeze the bag; all-in-ones with a recirculating pump typically 70–75. Commercial breweries hit 85–90 because their mills, lauter tuns and volumes are optimized for it — the figures are not comparable, and a homebrew recipe written for "75%" is a recipe written for one brewer's system.
Two things move it that aren't your fault. Big grain bills lower it: the grain absorbs the same liters per kilo, but each of those liters is stronger wort, so more sugar stays in the bed — expect a 1.090 beer to come in five to ten points under your session-beer number. Very hoppy beers lower it a little: the hop matter holds back wort, so more stays in the kettle. Neither is a problem; both are predictable, which is the point.
A consistent 68% you can predict is worth more than an 80% you hit once. The number's only job is to make the next Expected OG come true — so measure it every brew, save it, and watch the trend rather than the peak. If it swings ±5 between brews, the variable is almost always a volume you eyeballed, a crush that changed, or a sparge you rushed; the grain is very consistent, and your kettle hasn't moved.
How do you raise brewhouse efficiency?
In rough order of return: crush finer (the single biggest lever — a mill gap around 0.035–0.040 in / 0.9–1.0 mm for a cooler, finer still for BIAB); measure your volumes properly so you're improving the real number, not the reported one; sparge deliberately — batch spargers with equal runnings, fly spargers slowly with the bed submerged; mash pH in the 5.2–5.6 range (conversion is slower and lauters worse outside it); a full 60 minutes at temperature with a stir at 20; and less kettle loss — whirlpool, settle, and pour more of it into the fermenter (a little trub is fine). Then stop. Past the high 70s the extra points cost more attention than an extra pound of malt.