HesapHanem

Potting Soil Calculator

Enter your container size and count to see how many bags of soil you need.

How it is calculated

The tool works in litres. You give the volume of one container, the number of identical containers and the volume of one bag, all in litres. total volume = container volume × containers, then bags = ceil(total volume ÷ bag size), so any fraction of a bag is rounded up to a whole bag, while an exact fit (112 L in 28 L bags is exactly 4) is not rounded up further. The total is also shown in cubic feet with ft³ = litres ÷ 28.317. All three inputs must be greater than zero, otherwise no result is shown. The tool does not work out pot volume from diameter and height, and it adds no allowance for settling or for pots that are not filled to the rim. If your pots differ in size, run each size separately and add the bags up.

Worked example

Eight pots of 12 litres each, with soil sold in 28-litre bags (about one cubic foot). Total volume: 12 × 8 = 96.00 L. Bags: 96 ÷ 28 = 3.43, rounded up to 4 bags. In cubic feet, 96 ÷ 28.317 = 3.39 ft³. Four bags hold 112 litres, so about 16 litres stay unused for topping up.

Try this example →

Common mistakes

  • Entering the pot's diameter or height instead of its volume in litres. The first field is a volume, not a size.
  • Typing the bag size in quarts or cubic feet (8 or 1) while the pot volume is in litres, which gives a huge bag count. Convert the bag to litres first (1 ft³ is about 28.3 L).
  • Using the nominal volume of the pot instead of the soil it actually takes. A tapered pot filled to a few centimetres below the rim holds less.
  • Mixing different pot sizes in one run and averaging them by eye. Calculate each size separately and add the bags.
  • Forgetting that bag volume is sometimes quoted compressed or dry, so a bag may yield less or more than its label once opened.

About this calculator

Filling containers with potting soil comes down to a volume calculation: for a cylindrical pot, volume equals π × radius² × height, and gardeners with several pots of different sizes need the sum of each container’s volume before they know how much soil to buy. Because potting mix is sold by bag in fixed volumes — commonly 1 cubic foot, 8 quart, 20 quart, or 50 liter bags depending on the brand and region — the last step is converting the total volume needed into a whole number of bags, rounding up since partial bags aren’t sold.

This calculator takes the volume of one container in liters (work it out with the formula above if you only know the dimensions), the number of containers, and your bag size in liters. It computes the combined volume and converts it into the number of bags required, showing the total in liters and cubic feet, saving a trip back to the garden center for one more bag or an unopened bag left over. It’s the kind of quick estimate home gardeners, container growers, and landscapers reach for before a potting or repotting session, since soil volume needs scale directly with pot diameter squared — a modest increase in pot size uses noticeably more mix than it looks like it would.

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  • Editorial team

    To find a straight-sided pot's volume, use about 0.000785 × diameter² × soil depth, with both in centimetres, which gives litres: a 20 cm pot filled 18 cm deep holds about 5.65 L. Tapered pots hold less, and soil settles after watering. If you would like a mode that takes diameter and height directly, tell us which pot shapes you use.

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