Abv Dilution Calculator

ABV Dilution Calculator

Calculate exactly how much water to add to reach your target alcohol percentage.

Results

Understanding Alcohol Dilution

The ABV Dilution Calculator is an essential tool for distillers, home brewers, and mixologists. Whether you are "proofing down" a high-strength spirit like moonshine, making a liqueur from neutral grain spirits, or precisely adjusting a batch of punch, calculating the exact amount of water required is crucial for flavor and safety.

The Dilution Formula

Dilution follows a simple algebraic principle known as the Concentration-Volume formula:

C1 × V1 = C2 × V2

• C1: Initial ABV percentage
• V1: Initial volume of spirit
• C2: Target ABV percentage
• V2: Total final volume (Spirit + Diluent)

To find the amount of water to add, we calculate V2 – V1.

Practical Example: Proofing Down Spirit

Imagine you have 750ml of spirit at 95% ABV (C1) and you want to dilute it to a standard drinking strength of 40% ABV (C2).

1. V2 = (95 × 750) ÷ 40 = 1,781.25 ml (Total Volume)
2. Water to add = 1,781.25 – 750 = 1,031.25 ml

Important Tips for Success

• Always use distilled water: Minerals in tap water can cause "louching" (cloudiness) in your spirits.
• Account for contraction: When alcohol and water mix, the molecules pack more tightly, resulting in a slightly smaller volume than the sum of the parts. For most home applications, this calculator provides an excellent starting point, but professional distillers use proofing tables to account for thermal expansion and molecular contraction.
• Temperature matters: ABV readings are most accurate at 60°F (15.5°C). If your liquid is warm, your hydrometer reading will be higher than the actual ABV.

function calculateAbvDilution() { var v1 = parseFloat(document.getElementById('currentVolume').value); var c1 = parseFloat(document.getElementById('currentAbv').value); var c2 = parseFloat(document.getElementById('targetAbv').value); var resultDiv = document.getElementById('dilutionResult'); var errorDiv = document.getElementById('errorMessage'); var waterText = document.getElementById('waterRequiredText'); var totalText = document.getElementById('totalVolumeText'); // Reset display resultDiv.style.display = 'none'; errorDiv.style.display = 'none'; // Validation if (isNaN(v1) || isNaN(c1) || isNaN(c2) || v1 <= 0 || c1 <= 0 || c2 <= 0) { errorDiv.innerHTML = "Error: Please enter valid positive numbers for all fields."; errorDiv.style.display = 'block'; return; } if (c2 >= c1) { errorDiv.innerHTML = "Error: Target ABV must be lower than the current ABV. You cannot increase ABV by adding water."; errorDiv.style.display = 'block'; return; } // Logic: V2 = (V1 * C1) / C2 // Water to add = V2 – V1 var v2 = (v1 * c1) / c2; var addedWater = v2 – v1; waterText.innerText = "Add " + addedWater.toFixed(2) + " units of water."; totalText.innerText = "This will result in a total volume of " + v2.toFixed(2) + " at " + c2 + "% ABV."; resultDiv.style.display = 'block'; }