Potting Mix Calculator: Ratio and Volume
How much of each ingredient do I need? Enter your total volume and the parts of each ingredient (for example 2, 1, 1 and 0 for a 2:1:1 mix). Leave a part at 0 if the recipe has fewer ingredients. Ratios are by volume, not weight.
Updated
Report a problem
Formula
- Total parts = sum of the parts of every ingredient
- Volume of one part = total volume / total parts
- Volume of an ingredient = volume of one part x its parts
- Litres: 1 US quart = 0.946352946 L, 1 cubic foot = 28.316846592 L
Worked example
12 quarts of a 1:1:1 mix: total parts = 3, one part = 12 / 3 = 4 quarts, so 4 quarts of each ingredient (11.36 litres in all).
8 litres of a 2:1:1 mix: total parts = 4, one part = 2 L, giving 4 L, 2 L and 2 L.
10 litres of a 3:2:1:1 mix: total parts = 7, one part = 1.429 L, giving 4.286 L, 2.857 L, 1.429 L and 1.429 L.
1 cubic foot of a 3:1:1 mix: 5 parts, one part = 0.2 cubic feet, so 0.6, 0.2 and 0.2 cubic feet.
When to use it
Use it when you follow a recipe for container mix or seed starting and want to scale it up or down, whether you are filling a few pots or a wheelbarrow. Typical recipes combine a base such as peat or coir with perlite or sand for drainage and compost for nutrients, but the right mix depends on your plants.
Common mistakes
- Measuring by weight when the recipe is by volume. A litre of perlite weighs far less than a litre of compost.
- Using a different scoop for each ingredient.
- Packing peat or bark hard in the bucket. Measure loosely, then expect the mix to settle after wetting.
- Mixing units, such as quarts for one ingredient and litres for another.
How it differs from nearby calculators
This page splits a total into parts for small container batches. The raised bed soil calculator sizes the volume of soil for a whole bed, and the compost calculator covers a layer spread over the surface. The fertilizer NPK calculator is for adding nutrients once the mix is made.
Frequently asked questions
How do I turn a 1:1:1 potting mix ratio into amounts?
Add the parts (1 + 1 + 1 = 3), divide your total by that number to get the size of one part, then multiply by each ingredient's parts. For 12 quarts that is 12 / 3 = 4 quarts of each ingredient.
How much of each ingredient is in a 2:1:1 mix?
A 2:1:1 mix has 4 parts, so the first ingredient is half the volume and the other two are a quarter each. For 8 litres that is 4 L, 2 L and 2 L.
Is a part measured by volume or weight?
Potting mix recipes are normally by volume, using the same scoop, bucket or pot for every part. Dry ingredients also settle and compact, so measure loosely packed and expect the mixed volume to drop a little after wetting.
How many litres are in a quart or a cubic foot?
One US quart is 0.946352946 litres and one cubic foot is 28.316846592 litres. So 12 quarts is about 11.36 L, and 1 cubic foot split three ways is 0.333 cubic feet of each ingredient.
How much of each ingredient for 1 cubic foot of a 3:1:1 potting mix?
The recipe has 5 parts, so one part is 1 / 5 = 0.2 cubic feet. That gives 0.6 cubic feet of the first ingredient and 0.2 of each of the other two. One cubic foot is 28.32 litres.
How do I mix 20 litres of a 50:50 potting mix?
A 50:50 mix is a 1:1 ratio with 2 parts, so one part is 20 / 2 = 10 litres. Use 10 L of each ingredient.
How much of each ingredient for 40 quarts of a 5:3:2 mix?
The parts add up to 10, so one part is 4 quarts. That gives 20 quarts, 12 quarts and 8 quarts, which is about 37.85 litres in total.