How deep should pea gravel be for a border?

51 to 76mm, which is 2 to 3 inches. Mr. Mulch: one ton covers 120 square feet at 2 inches, 60 square feet at 4 inches.

How deep should a border be?

Q: How deep should mulch be for a border?

50 to 100mm, which is 2 to 3.9 inches. Mainland Aggregates: bark used for mulching should be spread at 50 to 100mm depth.

A border is a surface layer with nothing structural under it, so depth is about suppressing weeds and holding moisture rather than carrying load.

Published laid depths for a border, by material
Material	Depth	In inches	Where the depth comes from
Mulch	50 to 100mm	2 to 3.9 in	Mainland Aggregates: bark used for mulching should be spread at 50 to 100mm depth.
Pea gravel	51 to 76mm	2 to 3 in	Mr. Mulch: one ton covers 120 square feet at 2 inches, 60 square feet at 4 inches.

Material

Depth

In inches

Where the depth comes from

Mulch

50 to 100mm

2 to 3.9 in

Mainland Aggregates: bark used for mulching should be spread at 50 to 100mm depth.

Pea gravel

51 to 76mm

2 to 3 in

Mr. Mulch: one ton covers 120 square feet at 2 inches, 60 square feet at 4 inches.

Working out the quantity once you have the depth

Multiply the area by the depth for a volume, then by the material's bulk density for a weight. Each calculator below does it in the units that material is sold in, and each shows the density range its figure came from.

Mulch calculator200 to 300 kg/m3, 10 percent waste
Wood chip calculator260 to 400 kg/m3, 10 percent waste
Slate chippings calculator1400 to 1700 kg/m3, 10 percent waste
Pea gravel calculator1543 to 1670 kg/m3, 10 percent waste
Cobbles calculator1554 to 1900 kg/m3, 10 percent waste
Compost calculator400 to 949 kg/m3, 10 percent waste

Materials without a published depth for this use

No supplier read for this site publishes a laid depth for wood chip, slate chippings, cobbles and pebbles and compost on a border, so none is stated here. Their calculators take whatever depth you enter.