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IBU Calculator — International Bitterness Units

Calculate IBUs for your homebrew using Tinseth or Rager formulas.

Gravity of the wort during the boil

How We Calculate This

The Tinseth Formula

IBU = (W x AA/100 x U x 1000) / V, where W = hop weight (g), AA = alpha acid %, U = utilisation, V = volume (L). Utilisation = bigness factor x boil time factor. The bigness factor accounts for higher gravity worts reducing hop utilisation.

The Rager Formula

Rager uses a different utilisation curve based on a tanh function and applies a gravity adjustment for worts above 1.050. Both formulas give reasonable estimates — pick one and stick with it for consistency.

Frequently Asked Questions

Last updated: 2025-02-20

All calculations are estimates. Always verify values and adjust based on your equipment and ingredients.