BYTETOOLS

Raised Bed Soil Calculator

Work out how much soil your raised beds need in cubic feet, cubic yards, litres and bags, then split it by mix ratio into compost, peat or coir and vermiculite.

Beds to fill

For an L-shaped bed, split it into two rectangles that do not overlap — enter the long arm as length × width and the short arm as leg length × leg width.

58.67
Fill volume (cu ft)
64.53
With settling (cu ft)
2.39
Cubic yards
1,827
Litres

Mix and bag counts

The default is the classic thirds mix — one third compost, one third peat or coir, one third vermiculite. Shares are normalised, so they do not have to add up to exactly 100. Bag sizes are in cubic feet.

ComponentShareBag size (cu ft)Bag price ($)Volume (cu ft)BagsCost
Compost
21.4915$97.50
Peat or coir
21.498$112.00
Vermiculite or perlite
21.5511$242.00
Total10064.5334$451.50

Per bed

BedVolume (cu ft)LitresShare of total
Bed 153.331,51090.9%
Herb bed5.331519.1%

Volume = footprint × fill depth, where the footprint is length × width for a rectangle, π × radius² for a round bed, and the sum of two non-overlapping rectangles for an L. Fill depth is the soil depth, not the height of the frame — leave a couple of inches of freeboard so watering does not wash the mix over the sides. Bagged compost is sold by volume when dry and settles once wet, which is what the settling allowance covers. Estimates only.

What is the Raised Bed Soil Calculator?

The ByteTools Raised Bed Soil Calculator handles as many beds as you have, in rectangular, round or L-shaped form, with a quantity field so identical beds are entered once.

  • Rectangular, round and L-shaped beds, with a quantity field for identical beds
  • Volume in cubic feet, cubic yards, cubic metres and litres at the same time
  • Editable mix ratio with normalised shares — the thirds mix by default
  • Per-component bag size, bag count and cost, plus a grand total
  • Settling allowance for the drop a fresh mix takes when first watered
  • Per-bed breakdown and a copyable shopping list, all computed locally

How to use the Raised Bed Soil Calculator

  1. 1

    Choose imperial or metric units, your currency, and a settling allowance — 10% is normal for a fresh mix.

  2. 2

    Add a row per bed: name it, pick rectangular, round or L-shaped, set how many identical beds there are, and enter the dimensions and fill depth.

  3. 3

    Read the total fill volume in cubic feet or metres, cubic yards, and litres.

  4. 4

    Adjust the mix shares if you are not using the classic thirds, and set the bag size and price for each component.

  5. 5

    Copy the shopping list, and check the per-bed table to see which bed is using the most soil.

About the Raised Bed Soil Calculator

The ByteTools Raised Bed Soil Calculator handles as many beds as you have, in rectangular, round or L-shaped form, with a quantity field so identical beds are entered once. It multiplies footprint by fill depth, adds a settling allowance for the drop that happens the first time everything gets wet, and reports the total in cubic feet, cubic yards, litres and bag counts.

It then splits that volume by mix ratio. The default is the classic thirds — one third compost, one third peat or coir, one third vermiculite — but every share is editable and the numbers are normalised, so they do not have to add up to exactly 100. Each component gets its own bag size, bag count and price.

A per-bed table shows where the volume is going, which is useful when one deep bed quietly eats half the budget. Everything runs in your browser: no measurements are uploaded and nothing is stored.

Frequently asked questions

How much soil do I need for a 4x8 raised bed?

A 4 by 8 foot bed filled 10 inches deep needs 26.7 cubic feet, which is just under one cubic yard or about 755 litres. At 1.5 cubic feet per bag that is 18 bags, so a bulk delivery usually works out cheaper past two or three beds.

How deep should a raised bed be?

Six to eight inches suits salads and herbs, ten to twelve inches suits most vegetables, and eighteen inches or more is worth it for carrots, parsnips and anything with a deep taproot. Fill depth is the soil depth, not the height of the frame — leave freeboard for watering.

What is the best soil mix for raised beds?

The classic recipe is equal parts by volume of compost, a moisture-holding material such as peat or coir, and an aerating material such as vermiculite or perlite. That is the default here, but the shares are editable because good compost quality matters far more than hitting exact thirds.

How many bags of soil are in a cubic yard?

A cubic yard is 27 cubic feet, so it takes 18 bags at 1.5 cubic feet, 14 bags at 2 cubic feet, or 9 bags at 3 cubic feet. The calculator does this for whatever bag size you enter for each component of the mix.

Why does my raised bed soil sink after the first season?

Bagged material is sold dry and fluffed, and it compacts as it wets and as the organic fraction breaks down. Ten percent settling in the first watering is normal and more over the season, which is why beds want topping up with compost each spring.

Can I fill the bottom of a raised bed with something cheaper?

Yes — logs, branches and coarse woody material at the base of a deep bed cut the volume of bought mix considerably, and they hold moisture as they break down. If you do that, reduce the fill depth you enter here to only the soil layer above them.

Related tools