Pots and potting mix
Potting Mix Ratio Calculator: Amount of Each Ingredient
Enter the finished batch volume, then describe each ingredient in parts or percentages. The calculator instantly scales the recipe, and you can rename, add, or remove ingredients.
Calculator
Scale a mix to the batch you need
Enter a finished batch volume and edit the ingredient names and proportions. Results update as you type.
Before you calculate
What this estimate can tell you
In a recipe such as two parts base material, one part aeration material, and one part bark, a part is a relative volume rather than a fixed number of liters or gallons. This calculator scales that ratio to your target batch; it does not decide whether the recipe suits a particular plant, container, or growing environment.
How parts and percentages are scaled
In parts mode, add all parts and calculate target volume × ingredient parts ÷ total parts. In percentage mode, calculate target volume × percentage ÷ 100; all ingredients must total 100%. Liters, milliliters, US gallons, and US quarts change the displayed volume unit, not the recipe ratio.
Assumptions and limits
- All bulk ingredients are measured by volume with the same scoop, bucket, or volume unit; do not mix pounds or kilograms into a volume ratio.
- Results are theoretical loose ingredient volumes. Particle nesting, wetting, vibration, and compaction can change the final mixed volume.
- The calculator scales the recipe you enter. It does not recommend a ratio or determine whether a mix is appropriate for a particular plant.
Worked example
Example: 10 liters at a 2:1:1 ratio
A 2:1:1 recipe contains four total parts, so one part in a 10 L batch is 10 ÷ 4 = 2.5 L. The two-part ingredient needs 5 L, and each one-part ingredient needs 2.5 L. The arithmetic does not make 2:1:1 a universal plant recommendation.
FAQ
Common questions
What does a 2:1:1 potting mix ratio mean?
It divides four equal volume parts into 50%, 25%, and 25%. One part can be a cup, scoop, bucket, liter, or gallon, provided every bulk ingredient uses the same volume basis.
Do parts have to be whole numbers?
No. Ratios such as 1.5:1:0.5 work the same way: the calculator totals the values and uses each value's share. For hands-on mixing, you may prefer to scale the ratio to easier measuring numbers.
Can I combine pounds and gallons in one ratio?
Not reliably. Pounds measure weight and gallons measure volume. Potting ingredients have different bulk densities, and moisture changes weight, so a volume recipe should keep every bulk ingredient on a volume basis.
Why can the finished mix be smaller than the target volume?
Fine particles can settle into spaces between coarse particles, and wetting, vibration, or compaction can reduce volume. Use the result to prepare ingredients, then expect some real-world variation when filling containers.
Why must percentage mode total 100%?
Percentages describe the complete allocation of the batch, so all ingredients must add to 100%. If you only know relative values, parts mode avoids converting them to percentages first.
Calculation references
- Penn State Extension: Potting Media and Plant PropagationUsed to verify that horticultural mix recipes are commonly expressed in parts, percentages, or equal-volume containers and vary by purpose.
- University of Georgia Extension: Gardening in ContainersUsed to verify volume-based potting-mix ratios and the importance of uniform mixing.
- NIST: SI Units — VolumeUsed to verify the relationship between liters and milliliters.