Brewing · IBU Calculator
Enter your batch, boil gravity, and hop schedule to estimate bitterness in IBU with the Tinseth formula, plus BU:GU balance — live as you type.
Worked example
≈ 38 IBU
Longer boils bitter far more — edit the schedule live below.
Live calculator · Tinseth formula
Uses the Tinseth model, the most common homebrew IBU estimate. Real bitterness varies with hop form, age, boil vigour, and whirlpool/dry-hop additions, which contribute little measured IBU.
Estimated bitterness
Typical IBU by beer style
IBU guide
Bitterness comes from when and how much you hop, tempered by your boil gravity. This guide explains the Tinseth model and how to hit a style's target range.
The most common homebrew utilisation model.
A BU:GU ratio around here tastes balanced.
The long boil addition does most of the work.
Utilisation rises with boil time and falls with boil gravity, so long, low-gravity boils extract the most bitterness from a given weight of hops.
Set your units, batch size, and boil gravity, then enter each hop addition — amount, alpha acid percentage, and boil time. The calculator returns the IBU each addition contributes and the total, updating live as you adjust any field.
Enter the alpha acid figure from your hop packaging, since it varies by harvest. Use your boil gravity rather than the finished original gravity if you dilute afterward, because bitterness extraction happens during the boil.
An IBU is roughly one milligram of isomerised alpha acid per litre of beer. Alpha acids come from hops and only become bitter once heat isomerises them during the boil. The longer and hotter the boil, the more isomerisation, and the higher the IBU.
Measured bitterness is not the same as perceived bitterness. A malty, high-gravity beer can carry 60 IBU and taste balanced, while a dry pale ale at 35 IBU can taste sharply bitter. IBU is the objective anchor; balance comes from context.
For each addition, Tinseth multiplies the alpha acid concentration in the wort by a utilisation factor. That factor combines a bigness term — lower for denser wort — and a time term that rises quickly over the first 30 minutes of the boil and then flattens.
This is why a 60-minute addition contributes far more bitterness than a 10-minute one of the same weight, and why identical hops bitter a light beer more than a strong one. The calculator applies all of this automatically per addition.
The BU:GU ratio divides bitterness units by gravity units to judge balance before you brew. It is a fast sanity check that a recipe will not taste thin and harsh or cloying and flat.
Aim for the balance your style wants: malty beers sit low, hoppy beers sit high. Adjust hop timing and weight to move the ratio without changing the whole grain bill.
Light lagers and wheat beers sit low, around 8 to 18 IBU, letting malt and yeast character lead. Pale ales land 30 to 45, IPAs 40 to 70, and double IPAs can push past 100, where perceived bitterness plateaus even as the number climbs.
Dark beers like stouts and porters often measure 25 to 45 IBU, but roast bitterness from the malt adds to the impression, so they can taste more bitter than the number suggests. Use the chart in the calculator to aim for your style.
Common questions about bitterness, hop utilisation, and balance.
IBU stands for International Bitterness Unit, a measure of the concentration of isomerised alpha acids — the compounds from hops that taste bitter — in finished beer. One IBU is roughly one milligram of isomerised alpha acid per litre. Higher IBU means more measured bitterness, though perceived bitterness also depends on malt sweetness.
It uses the Tinseth formula, the most widely used homebrew model. For each hop addition it multiplies the alpha acid concentration by a utilisation factor that depends on boil gravity and boil time, then sums the additions. Longer boils and lower gravity extract more bitterness, which the formula captures.
Denser, sugar-rich wort extracts alpha acids less efficiently, so the same hops in a higher-gravity boil yield fewer IBU. That is why big beers need proportionally more hops for the same bitterness. Enter your boil gravity — not your original gravity if you top up afterward — for the most accurate estimate.
BU:GU compares bitterness units to gravity units (the last two digits of gravity). It gauges balance: around 0.5 is balanced, below 0.4 leans malty, and above 0.7 is firmly bitter. It is a quick way to judge whether a recipe will taste balanced before you brew it.
Very little measured IBU. Hops added at flameout, in the whirlpool, or as dry hops contribute aroma and flavour but isomerise few alpha acids, so this calculator focuses on boil additions. Late and dry hops still shape perceived bitterness even though the IBU number barely moves.
Tinseth is a solid planning estimate, not a lab measurement. Real IBU shifts with hop form and freshness, boil vigour, wort pH, and how you handle late additions. Use it to compare recipes and hit a target range rather than to predict an exact laboratory value.