Water to Add: 70% → 40% ABV
Standard volume method. Verify the final strength with a hydrometer before bottling.
Per 1 Litre
750mL water
Per 750 mL bottle
562mL water
Per 1 US gallon
2839mL water
Final volume / litre
1750mL
water to add = volume × (current ABV − target ABV) ÷ target ABV
= 1000 × (70 − 40) ÷ 40 = 750 mL per litre
Open the interactive ABV Dilution Calculator →
= 1000 × (70 − 40) ÷ 40 = 750 mL per litre
About this dilution
70% reflects strong hearts collected from a reflux or column still, while 40% is the legal minimum and standard bottling strength for most spirits. Bringing 70% down to 40% means adding roughly 750 mL of water for every litre of spirit, increasing the batch to about 1750 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 40% ABV. Measure at 20°C.
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Common questions
How much water do I add to dilute 70% ABV to 40%?
Add roughly 750 mL of water to each litre of 70% spirit to reach 40% ABV. The formula is water to add = volume times (current ABV minus target ABV) divided by target ABV.
Why should I verify the result with a hydrometer?
Ethanol and water contract slightly when mixed, so the real strength can sit just under the calculated figure. Always confirm with a calibrated alcoholmeter at 20°C before bottling.
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