Mash efficiency
Calculate the percentage of theoretical sugar yield your mash actually extracted, used to size grain bills for future batches.
Formula
Efficiency_% = (Actual_gravity_points × Batch_volume_gal) ÷ (Sum_of_grain_yield_points) × 100 where each grain contributes: weight_lb × ppg(yield)
Inputs
| Name | Unit | Description |
|---|---|---|
| SG | - | Post-boil specific gravity |
| V_gal | US gal | Post-boil batch volume |
| ppg | points/lb/gal | Maximum possible yield of each grain (Maris Otter ≈ 38, Crystal 60 ≈ 34, Chocolate ≈ 28) |
| W_lb | lb | Weight of each grain |
Outputs
| Name | Unit | Description |
|---|---|---|
| efficiency | % | Actual extract efficiency. Use this to scale future grain bills to your equipment. |
Worked example
Inputs:
- maris_otter_lb = 11.9
- maris_otter_ppg = 38
- crystal_60_lb = 0.9
- crystal_60_ppg = 34
- measured_OG = 1.058
- batch_gal = 5
Calculation:
Theoretical points = (11.9 × 38) + (0.9 × 34) = 452.2 + 30.6 = 482.8 Actual points = (1.058 − 1) × 1000 × 5 = 290 Efficiency = 290 ÷ 482.8 × 100 = 60.1%
Result:
60% mash efficiency — lower than ideal; check crush, mash temp and sparge
Sample values
| Brew system | Typical efficiency |
|---|---|
| No-sparge BIAB, coarse crush | 60-65% |
| BIAB, fine crush, mash-out | 70-75% |
| Batch sparge, 3-vessel | 72-78% |
| Fly sparge, 3-vessel, well-tuned | 80-85% |
| Commercial brewery (reference) | 88-92% |
Why this matters
If you don’t know your efficiency, you can’t size a recipe accurately. A recipe printed at 75% efficiency will undershoot OG by 20 gravity points on a system actually running 60% — that’s the difference between a 5% bitter and a 3.5% one.
How to improve
In rough order of impact:
- Crush. A finer crush exposes more starch surface to enzymes. If your homebrew shop’s mill is set coarse, ask for a closer setting or buy your own mill.
- Mash duration. A 60-minute mash is the minimum for full conversion. Iodine-test the wort if in doubt (black-blue colour means starch remains).
- Sparge volume and temperature. Hotter (76-78 °C) and slower sparges extract more. Don’t exceed 78 °C or you’ll extract tannins.
- Recirculate the first runnings. Vorlauf (slowly drain and pour back) clears the grain bed and adds 1-3% efficiency.
When to stop optimising
If you’re consistently at 70-75% on a homebrew system, that’s healthy. Chasing 85% requires equipment changes (proper sparge arm, pumps, recirculation). The energy is better spent on recipe iteration.