IBU Calculator - Hop Bitterness from Alpha Acids (Tinseth)

Every hop variety has an alpha acid number - this calculator turns it into bitterness you can taste

IBU (International Bitterness Units) measures the concentration of iso-alpha acids in beer - the compounds responsible for bitterness. The Tinseth formula takes three inputs per hop addition (weight, alpha acid percentage, boil time) and factors in wort gravity and batch volume. The result: a single number that tells you how bitter your beer will be.

How to use the IBU calculator - step by step

Post-boil volume - the amount of wort after the boil, in liters. Typical: 19-23 L (5-6 US gal).
Wort gravity (OG) - original gravity in SG. Higher gravity reduces hop utilization.
Number of additions - how many separate hop additions your recipe has (1-5).
Per addition: weight, alpha acids, boil time - check your hop package for alpha acid percentage.
Read results - total IBU, per-addition breakdown, BU:GU ratio and style classification.

Hop atlas - popular varieties and their alpha acids

Reference table for common hop varieties. Alpha acid ranges are typical crop averages - check your specific package for the exact number.

Hop variety	Alpha acids	Primary use	Flavor profile
Saaz	3-5%	Aroma	Spicy, herbal, earthy - classic Pilsner hop
Cascade	5-7%	Dual	Grapefruit, floral - the American craft hop
Centennial	9-12%	Dual	Citrus, pine - "Super Cascade"
Citra	11-13%	Aroma	Mango, passion fruit, tropical
Simcoe	12-14%	Dual	Pine, berry, earthy - versatile IPA hop
Mosaic	11-13%	Aroma	Berry, tropical, stone fruit - complex
Columbus / CTZ	14-17%	Bittering	Pungent, resinous - clean bittering
Magnum	12-16%	Bittering	Neutral, clean - the workhorse bittering hop
Galaxy	13-15%	Aroma	Peach, citrus, passion fruit - Australian
Nelson Sauvin	12-14%	Dual	White wine, gooseberry - New Zealand

IBU ranges by beer style

Beer style	IBU range	BU:GU	Character
Wheat Beer	8-15	0.2-0.3	Minimal bitterness
Pilsner / Lager	20-35	0.4-0.7	Balanced
Pale Ale / APA	30-45	0.6-0.8	Pronounced
IPA	40-70	0.7-1.0	Hop-forward
Stout / Porter	25-45	0.5-0.7	Hidden behind roasted malt
Double IPA	60-100	0.8-1.2	Aggressive
Barleywine	50-100	0.6-0.9	Strong, malt-balanced

Practical examples

Example 1: German Pilsner - 23 L, OG 1.048, 1 addition: 20 g Magnum (12% aa) at 60 min
Result: 19.2 IBU, BU:GU 0.40 - clean, balanced bitterness

Example 2: American Pale Ale - 23 L, OG 1.055, 2 additions: 25 g Centennial (10%) at 60 min + 20 g Cascade (6%) at 15 min
Result: 34.4 IBU, BU:GU 0.63 - pronounced bitterness with citrus aroma

Example 3: West Coast IPA - 23 L, OG 1.065, 3 additions: 35 g Columbus (14%) at 60 min + 25 g Simcoe (13%) at 15 min + 30 g Citra (12%) at 0 min
Result: 58.3 IBU, BU:GU 0.90 - aggressive bitterness, tropical aroma from whirlpool

Example 4: Dry Stout - 23 L, OG 1.042, 1 addition: 25 g East Kent Goldings (5%) at 60 min
Result: 20.8 IBU, BU:GU 0.50 - bitterness masked by roasted barley

Example 5: NEIPA - 23 L, OG 1.068, 2 additions: 15 g Magnum (14%) at 60 min + 40 g Galaxy (14%) at 0 min (whirlpool)
Result: 30.2 IBU, BU:GU 0.44 - low perceived bitterness despite heavy hopping

FAQ - Frequently asked questions

What is IBU and can you actually taste it?

IBU measures iso-alpha acid concentration in beer. Humans can distinguish bitterness differences up to roughly 100 IBU - beyond that, the palate saturates. Perception also depends on malt sweetness: 40 IBU in a lager tastes more bitter than 40 IBU in a heavy stout.

Pellet vs whole cone - is there an IBU difference?

Yes. Pellets give roughly 10-15% higher utilization than whole cones. This calculator assumes pellets (Tinseth standard). If using whole cones, multiply hop weight by 1.1-1.15 or reduce expected IBU by 10%.

What is the BU:GU ratio and why does it matter?

BU:GU is the ratio of bitterness (IBU) to gravity units (GU = (OG-1) x 1000). It describes beer balance. Below 0.5 = malt-forward, 0.5-0.7 = balanced, above 0.8 = hop-forward. A Pilsner has BU:GU around 0.7, while a NEIPA sits at 0.4 despite heavy hopping.

Does dry hopping add IBU?

Practically no. Dry hopping adds 0-5 IBU regardless of hop amount. Alpha acids require temperatures above 80C (176F) to isomerize. Dry hopping contributes aroma and flavor, not bitterness.

Why does wort gravity affect IBU?

Denser wort contains more dissolved sugars that interfere with alpha acid extraction and isomerization. At OG 1.080, hop utilization drops by about 15-20% compared to OG 1.040. That is why Imperial IPAs need significantly more hops than a lager for the same IBU.

What happens at 0 minutes boil time?

A 0-minute addition (flameout/whirlpool) means hops are added when the heat is turned off. The wort is still hot (80-95C) so some isomerization occurs, but very little - typically 1-5 IBU per addition. The main contribution is aroma and flavor, not bitterness.

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