How do you adjust hop weight for a different alpha acid?
Bitterness comes from alpha acid, and alpha acid is weight × AA%. So to get the same bitterness from a hop with a different alpha, keep the product the same:
your weight = recipe weight × recipe AA% ÷ your AA%
A recipe calls for 40 g at 4.0% and your packet says 4.6%: 40 × 4.0 ÷ 4.6 = 34.8 g. One ounce of 6% Cascade replaced with 10% Centennial: 0.60 oz. Because the IBU formulas scale linearly with alpha acid, matching alpha at the same boil time and volume matches IBUs exactly — Tinseth, Rager or any other. (Some guides call the product "AAUs" or "HBUs"; it's the same arithmetic.)
The same variety comes in at 4.5% one year and 6.5% the next, and a packet loses alpha in storage — a hop that's spent a year in a warm cupboard can be a fifth down. That fifth costs you: 10% hops that are now 8% need 25% more weight for the same bitterness. So this calculator is as much for "same hop, new packet" as for swaps: read the AA% every time, and if the packet is old and was stored warm, knock a point or two off it before you trust it.
When you should not match by alpha
Late additions are there for aroma and flavor, which come from the hop oils, not the alpha acids — and oil content doesn't track alpha. Swap a 5-minute ounce of 6% Cascade for 0.6 oz of 10% Centennial "to match the alpha" and you've cut the aroma nearly in half for a bitterness contribution that was a couple of IBUs anyway. For anything under about ten minutes, whirlpool or dry hop, use the recipe's weight and pick a hop that smells right. Between 10 and 30 minutes it's a judgment call; the calculator splits the difference and tells you.
No two varieties are the same hop. The chart below groups them by family so a swap keeps the beer recognizably itself; the notes flag the ones that don't really have a stand-in. If a recipe is built around a single hop's character — a Citra pale ale, a Saaz pilsner — expect a good beer that isn't quite that beer, and don't blame the arithmetic.
Hop substitution chart
Common swaps by aroma family, with typical alpha-acid ranges. Adjust the weight with the calculator above.
| Hop | Typical AA | Substitutes | Note |
|---|---|---|---|
| citrus/tropical | |||
| Cascade | 4.5–7% | Centennial, Amarillo, Ahtanum | |
| Centennial | 9–11.5% | Cascade, Chinook, Columbus | "Super Cascade" — Cascade at about half the weight for bittering |
| Amarillo | 8–11% | Cascade, Centennial, Simcoe | |
| Citra | 11–13% | Mosaic, Galaxy, Simcoe | no true match; Mosaic is closest |
| Mosaic | 11–13.5% | Citra, Simcoe, Galaxy | |
| Galaxy | 13–15% | Citra, Mosaic, Nelson Sauvin | passionfruit character is hard to replace |
| pine/resin | |||
| Simcoe | 12–14% | Amarillo, Mosaic, Summit | |
| Chinook | 12–14% | Columbus, Northern Brewer, Nugget | |
| Columbus / CTZ | 14–16% | Chinook, Nugget, Magnum | dank; Magnum only for bittering |
| clean bittering | |||
| Magnum | 12–14% | Warrior, Columbus, Nugget, Horizon | |
| Warrior | 15–17% | Magnum, Columbus, Nugget | |
| Nugget | 12–14% | Magnum, Columbus, Chinook | |
| Northern Brewer | 8–10% | Perle, Chinook, Magnum | woody/minty; the California common hop |
| noble/spicy | |||
| Perle | 7–9.5% | Northern Brewer, Magnum, Hallertau Mittelfrüh | |
| Hallertau Mittelfrüh | 3.5–5.5% | Liberty, Mt. Hood, Tettnang, Hersbrucker | |
| Tettnang | 3.5–5.5% | Saaz, Spalt, Hallertau Mittelfrüh | |
| Saaz | 2.5–4.5% | Sterling, Tettnang, Lublin | Sterling is the US stand-in |
| earthy/English | |||
| Fuggle | 3.5–5.5% | Willamette, Styrian Golding, East Kent Golding | |
| East Kent Golding | 4.5–6.5% | Fuggle, Styrian Golding, Progress | |
| Styrian Golding | 4.5–6% | Fuggle, East Kent Golding, Willamette | a Fuggle, botanically |
| Willamette | 4–6% | Fuggle, Styrian Golding, East Kent Golding | |
| unique | |||
| Nelson Sauvin | 11–13% | Galaxy, Motueka | white-wine character; substitutes are loose |
Ranges and swaps as commonly listed in growers' variety guides (Yakima Chief, Hop Union) and the BJCP guidelines — approximate; the packet wins. Match bittering additions by alpha (calculator above), aroma additions by weight.