How much potting soil for a 12-inch pot?

About 0.15 cubic feet — one 0.5 cu ft bag fills roughly three 12-inch pots.

Can I reuse last year's potting soil?

Yes — refresh it by mixing in 25–30% fresh compost or new potting mix each spring. Discard soil that's compacted or held diseased plants.

What's the best bag size for a raised bed?

2 or 3 cu ft bags for anything over 8 cu ft total. Below that, 1 or 1.5 cu ft bags are easier to handle.

How long does potting soil last in the bag?

1–2 years if kept dry and sealed. Wet bags develop mold and lose structure.

landscaping · 5 min read

Potting Soil Bag Size Guide

Potting soil bags come in six or seven common sizes. Here's how much each fills, and how to pick the cheapest combination for your job.

Potting soil is one of the few gardening materials where bag size actually varies wildly — from 8-quart pouches to 3-cubic-foot sacks. Picking the right size can cut cost by a quarter without changing what you plant.

This guide covers every standard size, how many containers each fills, and how to combine bag sizes for the lowest total cost.

Standard bag sizes

Bag size	Cubic feet	Approx liters
8 qt	0.27	8.8
16 qt / 0.5 cu ft	0.5	14.2
1 cu ft	1.0	28.3
1.5 cu ft	1.5	42.5
2 cu ft	2.0	56.6
3 cu ft	3.0	84.9

Note

Bag labels sometimes read in dry quarts (US) and sometimes in liters (EU / metric). One US dry quart ≈ 1.1 liters ≈ 0.038 cu ft.

Container fill chart

How many containers each bag fills, at typical planting depths:

Container size	Volume	0.5 cu ft bag	1 cu ft bag	2 cu ft bag
6" pot	0.05 cu ft	10	20	40
1 gal pot	0.14 cu ft	3–4	7	14
5 gal pot	0.7 cu ft	0	1	3
12" hanging basket	0.3 cu ft	1–2	3	6
Standard window box (36")	0.6 cu ft	0	1–2	3

Cost per cubic foot

Larger bags almost always beat smaller ones on price per cubic foot. Rough figures for premium potting mix:

Bag size	Typical price	Per cu ft
8 qt	$5	$18.50
1 cu ft	$9	$9.00
2 cu ft	$15	$7.50
3 cu ft (contractor)	$20	$6.66

Pro tip

If you need more than 4 cu ft, price out 2 cu ft bags vs bulk potting soil from a landscape yard. Above about 6 cu ft, bulk is often cheaper — but confirm it's a true potting blend, not just screened topsoil.

Choosing between potting mix, garden soil, and topsoil

Potting mix — peat, perlite, and bark, engineered for containers. No native soil.
Garden soil — for in-ground beds. Contains topsoil + amendments. Too heavy for pots.
Topsoil — screened dirt. Neither for containers nor for planting without amendments.

Warning

Never fill containers with garden soil or topsoil. Both compact under watering, drown roots, and defeat drainage.

Common mistakes

Buying the smallest bag at the register — cheapest sticker, most expensive per cubic foot.
Mixing 'garden soil' into pots because it was on sale.
Filling large containers with pure potting mix — for anything over 5 gallons, mix in bark chips or perlite to save cost and improve drainage.
Ignoring the mix's water-retention agents — some contain synthetic polymers that swell to 40× their weight.

Frequently asked questions

How much potting soil for a 12-inch pot?: About 0.15 cubic feet — one 0.5 cu ft bag fills roughly three 12-inch pots.
Can I reuse last year's potting soil?: Yes — refresh it by mixing in 25–30% fresh compost or new potting mix each spring. Discard soil that's compacted or held diseased plants.
What's the best bag size for a raised bed?: 2 or 3 cu ft bags for anything over 8 cu ft total. Below that, 1 or 1.5 cu ft bags are easier to handle.
How long does potting soil last in the bag?: 1–2 years if kept dry and sealed. Wet bags develop mold and lose structure.

Summary

Potting soil bag price scales inversely with size — the biggest bag is almost always the cheapest per cubic foot. Match bag size to project size and never fill containers with garden soil or topsoil.

Potting SoilGardening Garden SoilSoil CompostGardening

6 min read

Raised Bed Soil Calculator Guide

The right raised-bed fill isn't just topsoil — it's a blend that drains, holds moisture, and doesn't collapse in year two.

7 min read

How Much Topsoil Do I Need?

New lawns want 4–6 inches. Vegetable beds want 12 inches. Here's how to translate those depths into an accurate topsoil order.

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These results are estimates only. Confirm quantities, compaction, waste, and delivery requirements with your supplier or project professional before ordering materials.