Bed volume. One mix, split by ratio.
Measure your beds, subtract anything already in them, then split the total volume across the components you will actually buy.
Bed volume and mix shares
Combine bed volumes, then split one mix across your components.
Methodology
For each bed, area = length × width and net depth = full bed depth − existing fill. Net volume = area × net depth. Only the volume you are adding counts, so a bed that is already full adds nothing. This tool does not measure a yard or assess soil quality.
Total exact volume = the sum of all bed net volumes. Beds are combined before any allowance or rounding, so several small beds share one order instead of buying for each separately. No intermediate volume is rounded.
With a chosen allowance, target volume = total exact volume × (1 + settling ÷ 100). It is applied once to the combined total, not per bed and not per component. The starting 0% is not a recommendation; no universal settling rate is assumed.
Each component’s share = target volume × share ÷ 100; the shares must total 100%, so the split conserves the target volume exactly before rounding. Bags for that component = its share ÷ your bag volume, rounded up separately. Rounding up per component means purchased volume is usually larger than the target, and the mix ratio you actually receive can shift.
Worked example · illustrative inputs
32 ft²bed area
×11 innet depth
→29.33 ft³exact volume
With no existing fill and a 0% settling allowance, the bed holds about 29.33 ft³. Splitting it 60% topsoil, 30% compost and 10% aeration gives 17.6 ft³, 8.8 ft³ and 2.93 ft³. At example bag volumes of 1.5 ft³, 1 ft³ and 2 ft³, that is 12, 9 and 2 bags — 23 bags in total, covering 18 ft³, 9 ft³ and 4 ft³.
Those 23 bags hold 31 ft³ against the 29.33 ft³ needed, and the surplus is not shared evenly: topsoil is 0.4 ft³ over, compost 0.2 ft³ over, aeration 1.07 ft³ over. Because each component rounds up on its own, the delivered ratio moves away from the 60 / 30 / 10 you asked for. If the same bed already had 6 in of soil, net depth would be 5 in and the exact volume would drop to about 13.33 ft³; if it were filled to the top, the tool would report nothing to add.
The dimensions, the 60 / 30 / 10 split and the 1.5 / 1 / 2 ft³ bag volumes are arithmetic examples, not a soil recipe or a horticultural standard. Use the ratio and products you have decided on; this page gives no soil, drainage, nutrient or planting advice.
Frequently asked questions
Multiply the bed's length by its width, subtract the depth already filled, and multiply by the remaining depth. Repeat for each bed and add the volumes. Only the volume you are adding counts, so a partially filled bed needs less than its full internal volume.
This tool does not recommend one. Enter the shares you have decided on, as long as they total 100%. The 60 / 30 / 10 starting split is an arithmetic example that mirrors a common topsoil, compost and aeration structure, not a horticultural standard, and the page gives no soil or planting advice.
The shares divide one combined volume, so they must conserve it. If they total more than 100% the split would claim more material than the beds hold; if they total less, some of the volume would be unassigned. The tool shows the running total and blocks the calculation until it reaches 100%.
Bags are whole units and each component is rounded up on its own, so the purchase always meets or exceeds each component's share. The difference is shown per component and as a total, and it is why the delivered ratio can differ from the ratio you entered.
Only what you enter. Settling starts at 0% and is applied once to the combined volume, not per bed and not per component. Fresh mixes and loose fills can settle by different amounts, so use a figure you are comfortable with rather than one assumed here.
Yes. Metric mode uses meters for bed length and width, centimeters for depth and cubic meters for volume. Switching units converts the measurements, bag volumes and displayed result while preserving bag counts and the per-bag prices you entered.
No. It multiplies each component's bag count by the price you enter for that product. Delivery, tax, labor, and any minimum order or blending charge are excluded, and no supplier discount is inferred.
A volume split for one raised bed mix, using the buyer's own ratio, bag size and optional price. The 60/30/10 starting split and 1.5 / 1 / 2 ft³ bag sizes are arithmetic examples, not a horticultural recommendation, and no soil, drainage, nutrient or planting guidance is provided.
General reference that raised-bed growing media is commonly blended from topsoil, compost and an aeration component. This calculator does not adopt its suggested proportions, depths or amendments as a standard.
Authority for the cubic foot to cubic metre and inch to centimetre conversions used to keep US and metric results physically equal.
Last reviewed: October 5, 2026