Soil Calculator [Free Tool]

How much soil do you need?

Calculate the amount of soil needed for your raised garden bed, potting container, or garden container with this handy soil calculator.

Why is this important?

Determining how much potting soil you need is a good starting point before buying your ingredients. If you only need enough soil for one or two small houseplants, you’ll probably save money buying it premixed. But if you are potting trays of seeds or filling a lot of pots, it makes sense financially to mix your own.

A good point of reference is that a standard-sized wheelbarrow holds 3 cubic feet. You would need 3 cubic feet to fill 6 10″x12″ planters.

RELATED: Guide to Soil Components: Peat Moss, Perlite, Sand, Organic Matter, and Compost

Mixing potting soil

When you’re mixing your potting soil, you probably won’t be using the same measurement as you did when you purchased each of the ingredients (which are usually sold by the cubic foot). The exception is if you bought everything in one cubic foot bags; that would make it easier.

To make things more confusing, most DIY recipes call for mixing it by the bucket because it’s a much more manageable way to figure out the amounts. So rather than measuring by cubic feet when mixing your potting soil, you would be measuring by ratio.

Useful ratios:

1. General Potting Mix for Trees, Shrubs, Perennials, and Fruit:
   • 70% garden soil
   • 30% organic matter
2. General Potting Soil Recipe for Flowers, Tropicals, and Vegetables:
   • 6 gallons sphagnum peat moss or coir fiber
   • 4.5 gallons perlite
   • 6 gallons compost
3. Potting Soil Recipe for Houseplants:
   • 2 gallons sphagnum peat moss or coir fiber
   • 1.5 gallons perlite
   • 2 cups coarse sand
4. Simple Potting Mix Ratio:
   • 1:1:1 ratio of peat moss, perlite, and compost

When using these ratios, you can adjust the quantities based on the volume of potting soil you need to create. For example, if you need 10 gallons of potting mix, you would use 7 gallons of garden soil and 3 gallons of organic matter for the general potting mix mentioned in the first ratio.

How much potting soil do I need to fill a 5 gallon bucket?

If you are measuring your soil using 5 gallon buckets from home improvement stores, their 12.5 inch wide by 14.5 inch tall 5 gallon buckets hold approximately 1.03 cubic feet of soil.

DIY Soil-based Potting Mix Recipe

The DIY basic recipe for soil-based potting mixes is 1 part topsoil, 1 part garden soil, 1 part peat moss and 1 part perlite.

If you want to substitute the garden soil with pure compost, you would reduce the compost portion from 25% to 12.5% and increase topsoil and peat moss from 25% each to 37.5% each. You will also need to take additional steps (as outlined further up the page) to prep the compost so that ammonia and acid levels are reduced before it is added to the soil mix.

The modified recipe for soil-based potting mix would be 1.25 part topsoil, 1/2 part compost, 1.25 part peat moss and 1 part perlite.

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