Oak ageing calculator

How to use it

1. Choose how you're ageing. In a small barrel, or with pieces of oak in a jar or demijohn.
2. For a barrel, enter its size. The calculator compares its oak per litre with a 200 L barrel and estimates how much it will lose to evaporation.
3. For sticks or staves, enter how many, and the size of each, along with the volume of spirit.
4. For chips or cubes, choose the kind, weigh them, and enter the volume of spirit.
5. Taste, and keep tasting. Oak works fast at first. Taste every few days, and take the oak out when the spirit is right - you can always add more.

How it works

Barrels. A barrel's inside surface grows more slowly than its volume, so smaller barrels give each litre more oak. The calculator uses a barrel of standard proportions: a 200 L barrel has about 91 cm² of oak per litre, a 5 L barrel about 3.4 times as much. Evaporation (the angels' share) also rises with the surface: a 200 L barrel loses about 2% a year in a temperate cellar.

Chips, cubes and sticks. Spirit soaks right through small pieces of oak, so their surface area understates what they give - a few grams of chips per litre flavour a spirit in weeks. They are measured by weight per litre instead, against the amounts home distillers commonly use: about 2–8 g per litre is usual, less is light, more is heavy.

Oak does more than add colour and flavour: over time the spirit also slowly changes in the barrel as it breathes. Small barrels and chips speed up the first part much more than the second, which is why their results taste different from long ageing.

Worked examples

A 5 L barrel gives about 3.4 times the oak per litre of a 200 L barrel, and loses roughly 7% a year; a 20 L barrel about 2.2 times.

20 g of oak chips in 5 L is 4 g per litre - a usual amount. One stick 15 cm × 2 cm × 1 cm in the same 5 L weighs about 21 g, or 4.2 g per litre.

Questions

Do small barrels age spirit faster?

They add oak flavour and colour faster, because each litre touches more wood. The slower changes of long ageing don't speed up as much, so a year in a small barrel isn't the same as years in a large one.

How much oak should I use per litre?

Many home distillers use about 2–8 g of toasted chips or cubes per litre, tasting every few days. Start light: you can always add more, but you can't take oak flavour out.

Chips, cubes or sticks?

Chips give flavour fastest but can turn harsh; cubes and sticks are slower and rounder. Toast and char level matter as much as size.

Should I toast or char my own oak?

You can: a light toast brings vanilla and coconut, a heavier toast caramel and spice, and char smoke and colour. Use untreated, seasoned oak only.

What strength should I age at?

Commonly 55–65% ABV: strong enough to draw flavour from the wood well. Dilute to bottling strength afterwards with the proofing calculator.