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IBU calculator

Estimate a beer's bitterness (IBU) from its hop bill, using the Tinseth, Rager, or Garetz convention — a recipe estimate, not an official measurement.

The IBU Calculator estimates the bitterness — International Bitterness Units — of a beer from its hop bill: each hop addition's weight, alpha acid, and boil time, plus your batch volume and boil gravity. It's a recipe prediction you can lean on while you build a beer.

It's an estimate only. IBU prediction has no official government formula — a real IBU is a spectrophotometric lab result (ASBC). The calculators here are the industry-standard homebrew models, never valid for a tax or label filing. On the hub it sits in the Estimates (non-regulatory) section, and the calculator itself opens with a Non-regulatory estimate badge and a highlighted warning to that effect.

It's free, needs no account, and computes in your browser.

Open the calculator

  • On the public site: in the top navigation choose Tools, then — in the Estimates (non-regulatory) section — on the IBU Calculator card choose Open calculator.
  • Inside the app: in the navigation choose Tools, then on the IBU Calculator card choose Open calculator.

Choose a convention

Under Convention you can pick the hop-utilization model used for the estimate. Each option carries a one-line note on when it fits:

  • Tinseth — the default, the modern homebrew standard. A good all-round estimate; start here and stay consistent.
  • Rager — reads higher than Tinseth, especially for late additions, and is often preferred for pellet hops.
  • Garetz — reads lower — a conservative low-end estimate. It's a simplified form here: it applies Garetz's gravity/concentration adjustment but leaves out his elevation, yeast, and filtration correction factors (which this tool doesn't collect), so it isn't the full canonical Garetz model. The calculator says as much in the note under the option.

The calculator starts on Tinseth.

Estimate the bitterness

Before you start: have your hop bill ready — for each addition, its weight, its alpha acid percentage, and its boil time — plus your batch volume and, if you have it, your boil gravity.

  1. Under Convention, leave Tinseth selected or choose another model.
  2. From the Hop mass unit list, choose the unit you'll weigh hops in: Grams (g) (the default), Ounces (oz), Kilograms (kg), or Pounds (lb).
  3. Fill in the first hop addition's row under Hop additions: Hop mass, Alpha acid % (a number from 0 to 30), and Boil time (min).
  4. To add another addition, choose Add hop addition and fill in the new row. To drop a row, choose Remove beside it (you always keep at least one row).
  5. In Batch volume, enter your finished batch volume, and from Unit choose its unit (Milliliters (mL), Liters (L) — the default — U.S. gallons, Wine gallons, Barrels (31 U.S. gal), or Fluid ounces).
  6. In Boil gravity, enter your boil gravity if you have it (a number from 1 to 1.2). This field is optional — leave it blank and the calculator uses 1.050.
  7. Estimated total IBU, labelled with the convention in use, appears as soon as you've entered at least one complete addition and a batch volume. If your bill has more than one addition, a per-addition breakdown appears beneath the total.

A hop row only counts once its mass, alpha acid, and boil time are all valid numbers — a blank or half-filled row is simply skipped. A boil time of 0 (a flame-out, whirlpool, or dry-hop addition) contributes no bitterness.

Worked example

A single 60-minute bittering addition — 28 g of 5% alpha-acid hops in a 20 L batch at 1.050 boil gravity, on the default Tinseth convention:

  1. Hop mass unit: Grams (g)
  2. Hop mass: 28, Alpha acid %: 5, Boil time (min): 60
  3. Batch volume: 20, Unit: Liters (L)
  4. Boil gravity: 1.050

The calculator shows Estimated total IBU (Tinseth) 16.1.

When to reach for it

Reach for the IBU Calculator while you're designing or scaling a recipe and want to see roughly where the bitterness will land before you brew. Keep in mind it's a prediction from a utilization model, not a measurement — the real bitterness depends on your system, your hops, and your process, and only a lab IBU is exact. A note at the bottom of the calculator restates this, and the page-bottom disclaimer confirms it's a reference tool, never a system of record for a filing.