IBU Calculator (Tinseth)

Glenn Tinseth's model multiplies a gravity bigness factor, 1.65 x 0.000125 ^ (OG - 1), by a boil-time factor, (1 - e ^ (-0.04 x minutes)) / 4.15, to get hop utilization. It then scales that by the alpha acid concentration in the wort to give IBU.

Alpha acid is a percentage, hop weight is in grams, boil time is in minutes, batch volume is in litres and gravity is a specific gravity like 1.050. If you brew in gallons and ounces, convert first, since the metric formula assumes grams per litre.

Denser wort isomerizes fewer alpha acids, so the bigness factor 1.65 x 0.000125 ^ (OG - 1) shrinks as gravity rises. In the examples above the same 60 minute boil yields more utilization at 1.050 than at 1.060.

It estimates one addition at a time. Run the tool once per addition using each hop's alpha acid, weight and boil time, then add the IBU figures together to get the total bitterness for the recipe.

Use the post-boil batch volume in litres, which is the volume the finished bitterness ends up dissolved into. Using a larger pre-boil volume would understate the concentration and the resulting IBU.

Tinseth models a rolling boil, so it needs a positive boil time. Whirlpool, hop stand and dry hop additions extract bitterness on other curves, contribute little measurable IBU, and should be estimated separately rather than entered here with a zero or tiny boil time.

Tinseth is a widely used approximation, not a lab measurement. Real bitterness depends on hop age, form (pellet or whole), boil vigor, pH and trub, so treat the number as a recipe planning guide rather than an exact IBU.

Utilization is the fraction of a hop's alpha acids that isomerize into soluble bittering compounds, shown here as a percentage. Longer boils and lower gravity raise it, which is why a 90 minute charge uses far more of the hop than a 15 minute one.

Yes. The math runs in your browser and nothing about your recipe is uploaded or stored, so you can plan proprietary beers without them leaving your device.