Water to Add: 63% → 43% ABV
Standard volume method. Verify the final strength with a hydrometer before bottling.
= 1000 × (63 − 43) ÷ 43 = 465 mL per litre
About this dilution
63% is typical American barrel-entry strength, while 43% is a common premium bottling strength used by many whisky and rum brands. Bringing 63% down to 43% means adding roughly 465 mL of water for every litre of spirit, increasing the batch to about 1465 mL.
For casual reduction the standard volume method above is accurate enough. When bottling at an exact legal strength, switch to OIML Precise mode in the calculator, which corrects for the slight volume contraction that occurs when ethanol and water mix.
Verify before bottling: a calibrated alcoholmeter is the only way to confirm you have hit 43% ABV. Measure at 20°C.