What is the BU:GU ratio?

It is IBU divided by gravity units, where gravity units = (OG − 1) × 1000. A 1.052 beer has 52 gravity units; at 40 IBU the ratio is 40 ÷ 52 ≈ 0.77. It captures how bitter a beer tastes relative to its malt sweetness.

What ratio should my beer have?

Rough guides: malty lagers and milds 0.3 to 0.5, balanced ales 0.5 to 0.7, American pale ales 0.7 to 0.9, and IPAs 0.8 to over 1.2. Double IPAs and aggressively hoppy beers can exceed 1.0 comfortably.

Why use gravity units instead of plain OG?

Plain OG values like 1.052 cluster too closely to divide meaningfully. Gravity units (the digits after the decimal, scaled to whole numbers) spread the scale out so the ratio is a clean, comparable number across recipes.

Does a higher ratio always mean more bitter?

It means more bitter relative to malt body. A 1.090 barleywine at 60 IBU has a ratio of about 0.67 and tastes balanced despite high absolute IBUs, because the heavy malt masks bitterness. The ratio captures perception, not raw IBU.

Is BU:GU the same as the RIS or BMI index?

It is the most common balance metric, but not the only one. Some brewers prefer the Balance Value (RaiBU/RBV) which weights residual sugar from FG. BU:GU using OG is simpler and widely used in style references and is what this calculator reports.

BU:GU Ratio Calculator

The BU:GU ratio is a fast way to judge whether a beer recipe will taste malty, balanced, or hoppy before you brew it. It compares bitterness (IBU) against malt sweetness (gravity units), giving a single number you can match to a target style.

How it works

The ratio is simply:

BU:GU = IBU / gravity_units
gravity_units = (OG − 1) × 1000

A 1.052 wort has (1.052 − 1) × 1000 = 52 gravity units. If the recipe is 40 IBU, the ratio is 40 ÷ 52 ≈ 0.77 — an American-pale-ale balance.

The reason gravity units are used instead of the raw 1.0xx number is scale: OG values from 1.040 to 1.090 all start with “1.0”, so dividing by them gives indistinguishable results. Multiplying the decimal part to whole numbers spreads the scale into a meaningful range.

Typical style ranges

BU:GU	Character	Example styles
0.30–0.50	Malty, sweet	Munich helles, mild, Scottish ale
0.50–0.70	Balanced	Amber ale, ESB, märzen
0.70–0.90	Hop-forward	American pale ale, porter
0.90–1.20	Bitter	IPA, West Coast pale
1.20+	Aggressively hoppy	Double IPA, imperial pale

Worked example

You have an IPA recipe at OG 1.064 and 65 IBU:

gravity_units = (1.064 − 1) × 1000 = 64
BU:GU = 65 / 64 ≈ 1.02

A ratio just over 1.0 confirms a firmly bitter, hop-driven IPA — exactly what the style calls for. If you wanted a softer, more balanced impression you would either drop IBUs toward ~45 (ratio ~0.70) or raise the malt.

Tips and notes

The ratio describes perceived balance, not absolute bitterness. A big barleywine can carry 60+ IBU and still taste balanced because the malt masks it.
Use it as a planning sanity check: if your numbers fall far outside the target style band, revisit the hop schedule or grain bill before brew day.
It pairs naturally with an IBU calculator (compute IBU first, then check balance here) and with finished-gravity tools for full recipe profiling.