Free Alcohol Dilution Calculator

Calculating the precise amount of water or a weaker spirit required to achieve a target alcohol concentration is a common task for home distillers, tincture makers, and anyone working with high‑proof alcohol. This free alcohol dilution calculator online simplifies the process: you input the strength of your starting spirit, the strength of the diluting liquid (0% for water), the desired final percentage, and the volume of strong alcohol you have. The tool immediately returns the volume of diluent needed, and it can optionally display the volume lost due to alcohol contraction. Whether you are diluting 95% rectified spirit to make vodka or adjusting 91% isopropyl alcohol for disinfection, this spirit dilution calculator supports both forward and reverse calculations, making it equally useful for converting a known amount of strong alcohol to a target or determining how much strong alcohol is needed to fill a given final volume.

Step‑by‑Step Usage

1. Select the type of strong alcohol you have (e.g., 95% rectified spirit or 40% vodka).
2. Choose the diluent: water (0%) or a weaker spirit with a known lower percentage.
3. Set the target alcohol percentage – this must be lower than the strong alcohol’s percentage.
4. Enter the volume of strong alcohol you plan to use.
5. The calculator instantly shows how much diluent to add. If you enable the contraction option, it also provides the net volume loss.

The Dilution Equation (Pearson’s Square)

The math behind the calculator is based on a simple mass‑balance formula often called the cross method. Let

• $A$ = alcohol concentration of the stronger spirit (vol%)
• $B$ = alcohol concentration of the weaker spirit or water (vol%)
• $C$ = desired final concentration (vol%)

Then

$$D = C - B \quad \text{(parts of strong alcohol)}$$ $$E = A - C \quad \text{(parts of weak spirit/water)}$$

The ratio $D : E$ tells you how many parts of strong and weak liquid to mix. For a known volume of strong alcohol $V_{\text{strong}}$, the required volume of diluent is

$$V_{\text{weak}} = \frac{E \times V_{\text{strong}}}{D}$$

Example: Suppose you have 200 mL of 95% alcohol and want to dilute it to 40% using water. Here $A = 95$, $B = 0$, $C = 40$, so $D = 40$ and $E = 55$. Then

$$V_{\text{weak}} = \frac{55 \times 200}{40} = 275\ \text{mL}$$

Add 275 mL of water to the 200 mL of strong alcohol to obtain approximately 475 mL of 40% alcohol (actual volume may be slightly less due to contraction).

Sweetening Your Homemade Spirit

After dilution, many home recipes (especially tinctures) require sweetening. The calculator does not prescribe sweetness, but the following guidelines help you choose.

Sweetness Level	Sugar per Litre of Solution (g)
Dry	≤ 50
Semi‑dry	51–120
Semi‑sweet	121–220
Sweet	221–330
Liqueur / Crème	> 331

Note that honey is about 30% less sweet than sugar by weight, so you may need more honey to achieve the same sweetness. Also, adding sugar increases the total volume:

• 100 g of sugar occupies approximately 60 mL.
• 100 g of honey occupies approximately 75 mL.

Keep these volume increases in mind when calculating final batch sizes.

Alcohol Contraction

When alcohol and water are mixed, the total volume decreases slightly because some alcohol molecules settle into gaps between water molecules. This phenomenon, known as alcohol contraction, means the final volume is always a little less than the sum of the individual volumes. The table below shows approximate volume losses for 1 L of mixture at various concentrations.

Total Volume	Alcohol Concentration	Volume Lost
1 L	10%	6 mL
1 L	20%	15 mL
1 L	30%	24 mL
1 L	35%	26 mL
1 L	40%	29 mL
1 L	50%	31 mL
1 L	60%	31 mL
1 L	70%	27 mL
1 L	80%	20 mL
1 L	90%	10 mL

The maximum contraction occurs around 50–60% alcohol, where up to 31 mL per litre is lost. For most home‑dilution tasks the loss is small, but it can matter when precision is critical. Using the calculator’s contraction option lets you account for this reduction.

A Versatile Tool for Every Dilution Task

Whether you need a spirit dilution calculator for adjusting proof, a free alcohol percentage calculator for blending liquors, or simply want to convert isopropyl alcohol to a safer concentration, this online tool handles all common scenarios. Its built‑in contraction estimation and ability to work with any combination of strengths make it indispensable for both hobbyists and professionals.