Brewing Reference Tables

Strength and attenuation

OG	FG	ABV	Apparent attenuation
1.04	1.008	4.2%	80%
1.05	1.01	5.25%	80%
1.06	1.012	6.3%	80%
1.07	1.014	7.35%	80%
1.09	1.02	9.19%	77.78%

Attenuation is the more useful diagnostic of the two: ABV tells you how strong the beer is, attenuation tells you whether the fermentation did what it was meant to. Compare it against your yeast strain’s published range rather than judging it in isolation.

Bitterness by boil time — 30 g at 10% AA in 20 L at 1.05

Boil time	IBU
90 min	37
60 min	34.6
30 min	26.6
15 min	17.2
5 min	6.9

The returns fall away sharply: 5 minutes gives 6.9 IBU and 90 gives 37, so tripling the longest boil adds very little. That is why the 60-minute bittering addition is conventional, and why late additions are about aroma rather than bitterness.

The same hops in a stronger wort — 60 minutes throughout

Boil gravity	IBU
1.04	37.9
1.05	34.6
1.06	31.6
1.08	26.4

Identical hops, identical time: 37.9 IBU at 1.04 against 26.4 at 1.08. Tinseth penalises high-gravity boils, so making a recipe stronger without touching the hop bill quietly makes it sweeter and less balanced.

Priming sugar — 19 L to 2.4 volumes

Beer temperature	CO₂ already in it	Corn sugar	Table sugar
4 °C	1.48 vol	69.66 g	63.39 g
10 °C	1.2 vol	91.31 g	83.09 g
15 °C	1.01 vol	105.75 g	96.23 g
18 °C	0.92 vol	112.85 g	102.69 g
21 °C	0.84 vol	118.77 g	108.08 g
24 °C	0.77 vol	123.51 g	112.4 g

Warm beer has already lost most of its dissolved CO₂, so it needs far more sugar — 123.51 g at 24 °C against 69.66 g at 4. Use the warmest temperature the beer reached after fermentation finished, not the temperature on bottling day: CO₂ driven off during a warm spell does not return when the beer cools.

Bottle only after two stable hydrometer readings days apart, and keep anything above about three volumes in bottles rated for it. Over-primed or unfinished beer is how bottles burst.

Colour — 5 kg pale malt plus roast at 500 °L

Roast added	Share of grist	MCU	SRM
0 kg	0%	6.26	5.25
0.05 kg	1%	16.69	10.29
0.1 kg	2%	27.12	14.35
0.2 kg	3.8%	47.99	21.23
0.3 kg	5.7%	68.85	27.19
0.5 kg	9.1%	110.58	37.63

A grist of pale malt alone sits at 5.25 SRM — pale gold. Adding 0.5 kg of roast, just 9.1% of the grain, takes it to 37.63. Morey’s exponent is below one, so colour saturates: past about 40 SRM the eye cannot tell one beer from another, and more roast changes flavour rather than appearance.

Strike water — 5 kg of grain at 20 °C, mashing at 66 °C

Water : grain	Strike at	Water
2 L/kg	75.43 °C	10 L
2.5 L/kg	73.54 °C	12.5 L
3 L/kg	72.29 °C	15 L
3.5 L/kg	71.39 °C	17.5 L
4 L/kg	70.72 °C	20 L

A thick mash has less water to carry the heat, so it needs a bigger head start — 75.43 °C at 2 L/kg against 70.72 °C at 4. Change your ratio and keep the old strike temperature and you will miss the mash by several degrees.

The formula accounts for grain and water only. A cold mash tun absorbs several degrees on the first mash of the day — preheat it, or measure your own correction over a few batches.