Fortification Spirit Addition Calculator

Work out fortification spirit addition instantly with clear inputs, formula shown and shareable results.

About Fortification Spirit Addition Calculator

Fortification is a two-component alcohol balance: spirit volume = wine volume x (target - wine ABV) / (spirit ABV - target). Fortifying a fermenting must arrests fermentation by killing the yeast, which is how port and other sweet fortified wines retain residual sugar.

Formula

Fortification blend

Spirit volume = wine volume x (target ABV - wine ABV) / (spirit ABV - target ABV)

Worked example

With the default values below, Fortification Spirit Addition Calculator returns Fortifying Spirit Required of 129.870. Change any input above and every figure here is recalculated in your browser.

Inputs used

Wine Volumeminimum 0 L: 1,000 L
Wine Alcoholaccepts 0–30 %: 9 %
Fortifying Spirit Alcoholaccepts 0–100 %: 96 %
Target Alcoholaccepts 0–30 %: 19 %

Results

Fortifying Spirit Required: 129.870
Final Blend Volume: 1,129.870
Pure Alcohol In Blend: 214.675
Blend Feasibility: Blend achievable

Step by step

1Values used
2Fortification blend
3Fortifying Spirit Required= 129.870
4Final Blend Volume= 1,129.870
5Pure Alcohol In Blend= 214.675
6Blend Feasibility= Blend achievable

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Production and fortification of alcoholic beverages is licensed and subject to excise duty. Alcohol content must be verified by an approved method.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Production and fortification of alcoholic beverages is licensed and subject to excise duty. Alcohol content must be verified by an approved method.

Frequently Asked Questions

When is the spirit added?

For sweet styles, during fermentation once the desired sugar remains — around 6-8% ABV for port. For dry styles such as fino sherry, after fermentation is complete.

Do volumes add exactly?

Not quite. Mixing ethanol and water causes a small volume contraction, so the actual blend is marginally less than the sum. For custody and duty purposes, alcohol tables must be used.