All Grain OG, FG & ABV Calculator
Plan your brew day with confidence. Enter your grain bill, volumes, and system efficiency, and this tool predicts your Original Gravity, Final Gravity, and ABV before you heat a single litre of strike water.
New to this? The defaults below are a working example (a ~5.5 gallon pale ale). Change the numbers to match your recipe and watch the results update instantly. A short how-to sits directly under the calculator.
1. Batch Data
2. Grain Bill
Add each fermentable and its weight. "Potential" is the average sugar yield in points per pound per gallon (PPG); the grey figure is that grain's share of the total grist.| Weight | Fermentable | Potential |
|---|
Your Calculated Targets
How To Use This Calculator
Step 1 — Set your batch data
Choose your units, then enter three numbers about your system: the wort you collect before the boil, the volume that ends up in the fermenter, and your brewhouse efficiency. If you have never measured efficiency, start at 70% and refine it after your first brew.
Step 2 — Build your grain bill
Add each malt, sugar, or extract and its weight. The calculator already knows the typical PPG for common fermentables; for anything unusual, choose "Custom" and type the PPG from the maltster's spec sheet. The grey percentage tells you how much each grain contributes to the total grist — handy for keeping specialty malts in check.
Step 3 — Read your targets
The four tiles update live. The most useful one is Est. Pre-Boil OG: measure your gravity right before the boil, and if it matches, the rest of the brew is on rails. If it is low, you know now — not two weeks later — that you can extend the boil or add a little DME to rescue the batch.
Step 4 (pro move) — Reverse-engineer the recipe
Don't just accept a result. Set your target OG in your head (say 1.050 for a pale ale), pick a style above to see its range, then nudge your base-malt weight up or down until "Est. OG" lands on target. You are now brewing to your system, not to a generic recipe sheet.
The Maths Behind The Numbers
There is no magic here — just four short steps that every brewing app runs under the hood. Understanding them makes it obvious why a number moves when you change an input.
1. Gravity points from the grain
Every fermentable has a maximum sugar potential measured in PPG (points per pound per gallon). Multiply each grain's weight by its PPG and add them up to get your total available points.
Total points = Σ (weight in lb × PPG)2. Apply your efficiency
You never extract 100% of that sugar. Brewhouse efficiency scales the total down to what actually makes it into your kettle.
Usable points = Total points × (efficiency ÷ 100)3. Spread points across your volume
Gravity is just sugar concentration — the same points in less water read higher. Dividing usable points by volume gives the gravity; the pre-boil reading uses your kettle volume, the OG uses your fermenter volume.
OG = 1 + ( usable points ÷ volume in gal ) ÷ 10004. Ferment down to FG, then find ABV
Yeast eats a percentage of the sugar (its apparent attenuation), leaving the final gravity. The gap between OG and FG is the alcohol.
FG = 1 + [ OG points × (1 − attenuation) ] ÷ 1000ABV % = (OG − FG) × 131.25
Metric entries are converted internally (kg → lb, L → gal) before the points maths, so the results are identical whichever units you choose.
Reference: Typical Style Targets
A quick sense-check for where common styles usually land. Ranges are approximate and drawn from broadly accepted style guidelines — treat them as guard rails, not rules.
| Style | OG | FG | ABV |
|---|---|---|---|
| Session / Ordinary Bitter | 1.032–1.040 | 1.007–1.011 | 3.2–3.8% |
| American Pale Ale | 1.045–1.060 | 1.010–1.015 | 4.5–6.2% |
| American IPA | 1.056–1.070 | 1.008–1.014 | 5.5–7.5% |
| Stout (Dry / Irish) | 1.036–1.050 | 1.007–1.011 | 4.0–5.0% |
| Hazy / New England IPA | 1.060–1.075 | 1.010–1.016 | 6.0–7.5% |
| Saison | 1.048–1.065 | 1.002–1.008 | 5.0–7.0% |
| Pilsner / Lager | 1.044–1.056 | 1.008–1.013 | 4.4–5.4% |
| Imperial Stout | 1.075–1.115 | 1.018–1.030 | 8.0–12.0% |
Reference: Fermentable Potential (PPG)
These are the average PPG values built into the calculator. Real yield varies by maltster and harvest, so check the spec sheet when precision matters and use the "Custom" option to override.
| Fermentable | PPG | Notes |
|---|---|---|
| 2-Row / Pale Malt | 37 | Workhorse base malt for most ales. |
| Maris Otter | 38 | Rich, biscuity British base malt. |
| Pilsner Malt | 37 | Clean, pale base for lagers. |
| Vienna / Munich | 37 | Adds malty depth and colour. |
| Wheat Malt | 38 | Boosts body and head retention. |
| Crystal 10L–80L | 34 | Caramel sweetness and colour. |
| Crystal 120L+ | 33 | Dark fruit, toffee, deep colour. |
| Chocolate / Roast Barley | 25 | Roast, coffee, colour; low yield. |
| Flaked Oats / Wheat | 32 | Body and silky mouthfeel. |
| Dextrose (Corn Sugar) | 46 | 100% fermentable; thins the body. |
| DME (Dry Malt Extract) | 44 | Great for gravity boosts. |
| LME (Liquid Malt Extract) | 36 | Extract brews and top-ups. |
The Architecture Of The Grain Bill
All-grain brewing is, at heart, an extraction exercise: you wash sugar off crushed husks with hot water. This calculator is the blueprint for that extraction. Without it, you are building a house without a tape measure — you might end up with something that stands, but the proportions will be off. Working the numbers before you heat your strike water is what moves you from "making soup" to engineering flavour.
The real prize is consistency. Once you know your system yields, say, 72% efficiency, you can take a recipe built for a commercial brewery and scale it perfectly to your 5-gallon setup. You are no longer guessing — you are translating. Ten pounds of Maris Otter will land on a predictable gravity on your gear every single time, and that repeatability is the hallmark of a confident brewer.
The pitfall is treating the calculator as a guarantee rather than a model. Real brewing has variables maths can't see: channelling in the mash tun, humidity nudging your boil-off rate, trub losses in the kettle. Most efficiency swings come down to your crush (pictured above). Too wide a mill gap leaves sugar behind and drops your efficiency; too fine and you risk a stuck sparge. The calculator assumes a standard crush — your mill sets the reality.
The jump from pre-boil gravity to OG is pure evaporation — the boil concentrates everything. Know your kettle's boil-off rate and you can hit volume and ABV at the same time. Boil too hard and you finish with less beer, stronger than planned; simmer too gently and you get weak, watery beer at the wrong volume.
Ultimately these numbers are targets, not laws. Use the calculator to set the course, then use your hydrometer and thermometer to navigate the brew day. Miss your pre-boil gravity? Don't panic — boil longer, add water, or tweak the hop schedule. The calculator hands you the map; you are still the one driving.
Quick Glossary
- Original Gravity (OG)
- The density of your wort before fermentation, relative to water (1.000). Higher OG means more sugar and, usually, more alcohol.
- Final Gravity (FG)
- The density after the yeast has finished. The gap between OG and FG is what became alcohol.
- ABV
- Alcohol by volume — the percentage of the finished beer that is alcohol.
- PPG (Points per Pound per Gallon)
- The maximum sugar a fermentable can contribute: one pound in one gallon at 100% extraction.
- Brewhouse Efficiency
- The share of the grain's total potential sugar that actually makes it into your fermenter. Reflects your whole process, from crush to kettle.
- Apparent Attenuation
- The percentage of sugar the yeast ferments. Higher attenuation gives a drier, stronger beer and a lower FG.
- °Brix / °Plato
- An alternative sugar scale (roughly interchangeable), often read from a refractometer. Shown alongside the gravity figures for convenience.
Frequently Asked Questions
What efficiency should I use if I've never measured mine?
Start at 70%. It is a safe middle-ground for a typical homebrew setup. After your first brew, compare your measured OG to the prediction and adjust the efficiency until the calculator matches your reality.
My measured gravity came in lower than predicted. What went wrong?
Almost always crush or volume. A coarse crush leaves sugar locked in the husk, and over-estimating your kettle volume dilutes the reading. Tighten your mill gap or calibrate your volume markings, then lower the efficiency setting to reflect your real yield.
Why are there two OG numbers?
Pre-boil OG is measured in the kettle before the boil, when the wort is more dilute. As water evaporates during the boil, the sugar concentrates and the gravity rises to your OG (into the fermenter). The pre-boil figure is your early warning system on brew day.
Does this work for extract or partial-mash brews?
Yes. Add DME or LME as a fermentable and set efficiency to 100% — extract sugar is already dissolved, so there is no mash step to lose it in. For a partial mash, keep your normal efficiency on the grain and add the extract separately.
How accurate is the ABV figure?
The (OG − FG) × 131.25 formula is a well-established approximation that is close enough for almost all homebrewing. It drifts slightly high on very strong beers, but for anything under about 8% it is reliable.
