Dilution & blending

Every liquid can be entered by litres or by weight, at its actual temperature. Everything is computed in mass (temperature-proof), litres are corrected for thermal expansion, and volume contraction on mixing comes from the ethanol-water density table.

Dilute to target ABV

Stock quantity

Unit

Stock temp °C

Stock ABV %

Target ABV %

Water temp °C

ABV is the 20 °C value — correct your alcoholmeter reading for temperature before entering it. Weigh where you can: kg needs no temperature correction at all. Check with a calibrated alcoholmeter at 20 °C before bottling.

Blend two stocks

A quantity

Unit

A ABV %

A temp °C

B quantity

Unit

B ABV %

B temp °C

LPA = litres of pure alcohol (called LAL in Australia and some other countries) — ethanol at 0.789 kg/L, 20 °C.
Litres change with temperature; kilograms don't. A litre entered at 35 °C is converted to mass using the density at 35 °C, then all arithmetic happens in mass.
Temperature correction: density slope interpolated between water (−0.00023 kg/L per °C) and ethanol (−0.00085) around 20 °C — good to a few parts in 10,000 over ~10-35 °C.
Final volumes are quoted at 20 °C, the legal reference for ABV and excise volume.
Mixing 50 L of water into 50 L of high-proof spirit yields noticeably less than 100 L — the contraction is real and the density table captures it.