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PPG means points per pound per US gallon. Check the malt analysis sheet when available; 36 PPG is an example potential, not a universal value.
This calculator estimates original gravity from a grain bill using gravity points, malt potential and your measured mash efficiency. The previous version incorrectly divided US-unit gravity points by an extra density factor; that understated OG. The corrected calculation is shown below so you can check every result by hand.
The corrected original-gravity formula
Total gravity points = grain weight (lb) × malt potential (PPG) × mash efficiency. Divide that total by final wort volume in US gallons, then convert the result to specific gravity: OG = 1 + (points per gallon ÷ 1,000).
This is the same gravity-point relationship described by Brew Your Own’s gravity calculation guide. Malt potential and efficiency are separate: the malt’s laboratory potential is the theoretical contribution, while efficiency represents what your brewhouse actually collects.
Worked example: 10 lb of grain in 5 gallons
- 10 lb × 36 PPG = 360 potential gravity points.
- 360 × 75% mash efficiency = 270 collected points.
- 270 ÷ 5 gal = 54 points per gallon.
- 54 points becomes an estimated OG of 1.054.
Choose realistic inputs
Malt potential (PPG)
Use the coarse-grind or supplier value for the actual malt when you have it. A generic 36 PPG is only a planning example. Different base, crystal and roasted malts do not contribute the same potential extract.
Mash efficiency
Use your own recent batches rather than copying another brewer’s efficiency. If you do not yet have a measured value, start with a conservative estimate and replace it after you compare predicted gravity with cooled, temperature-corrected hydrometer readings. The American Homebrewers Association efficiency reference explains the difference between conversion, lauter and brewhouse efficiency.
Final wort volume
Use the volume at which you want the OG estimate. Pre-boil and fermenter volumes are not interchangeable; evaporation and kettle losses change volume and therefore gravity.
Why the measured OG can differ
- The grain’s real extract potential differs from the default.
- Your crush, mash conversion, lautering and losses change actual efficiency.
- The sample was not fully mixed or was read at a different temperature from the hydrometer’s calibration.
- The entered volume is pre-boil while the reading is post-boil, or vice versa.
Treat the result as a recipe-planning estimate. Record predicted and measured values for each batch; your own stable efficiency is more useful than a generic percentage.
Grain versus malt extract
This page applies mash efficiency to a grain bill. Dry and liquid malt extracts are already concentrated wort and should be calculated from their supplier yield without applying mash efficiency. Briess’s current extract usage sheet, for example, publishes product-specific amounts for target gravities. Do not enter DME or LME here as though it were mash grain.
