Free calculator
Raised Bed Soil Calculator
Use this raised bed soil calculator to estimate how much soil and compost you need to fill garden beds. Enter bed length, width, height, the number of beds, waste, bag size, and a compost blend share to get cubic feet, cubic yards, bags, and a printable material list.
EstimateEstimate only; soil settling, moisture, blend ratio, and supplier material vary by project and bed.
Project inputs
Estimate
1.04 cubic yards of raised bed soil
1 bed(s) at 32 sq ft and 10 inches deep need about 28 cubic feet, 1.04 cubic yards, or 19 bags of fill.
Printable material list
Estimate- Bulk raised bed mix1.04 cu yd5% extra for settling
- Bagged mix19 1.5-cu ft bagsuse the bag label when different
- Compost portion8.4 cu ft30% of the blend
- Base soil portion19.6 cu fttop soil or garden soil for the remainder
Estimate only. Soil settles after watering, and the right blend depends on the plants, drainage, and supplier material.
Visible defaults
Assumptions
- Bed volume uses the fill height you enter, not the full frame height.
- Default settling allowance is 5 percent because soil drops after watering.
- Compost blend share defaults to 30 percent of the total volume.
- Bag count is based on the bag size you enter and rounds up.
Math
Calculation details
- Bed volume = length x width x height in feet.
- Total cubic feet = bed volume x number of beds.
- Cubic yards = cubic feet / 27.
- Compost portion = total cubic feet x blend share.
What this raised bed soil calculator does
Filling a raised bed almost always takes more soil than it looks, which is why people run short on the first trip. This calculator converts the inside length, width, and fill height of a bed into cubic feet and cubic yards, multiplies by the number of beds, and splits the total into a compost share and a base soil share so you can plan a blend rather than buy one product.
It is meant for vegetable beds, flower beds, and garden boxes. It does not judge soil quality or what a specific plant needs, but it does give a realistic volume and a printable list you can take to a garden center or use to size a bulk delivery.
Bed size and fill height
Measure the inside dimensions of the bed, not the outside of the frame, because the boards take up space. For fill height, use the depth of soil you actually plan to add. Many growers leave an inch or two below the rim so soil and mulch do not wash over the edge when watering.
Deeper is not always better. Most vegetables are happy with 8 to 12 inches of good soil, and a very deep bed can be filled partly with coarse material at the bottom. If you plan to fill only the top portion with quality mix, enter that depth as the fill height instead of the full frame height.
Choosing a soil blend
A common raised bed approach mixes a base of top soil or garden soil with compost for nutrients and structure. This calculator uses a compost blend share so you can see how much of each to buy. A share around a quarter to a third of the total is a typical planning range, with the rest as base soil.
More compost is not automatically better. Too much can hold water, settle heavily, and concentrate nutrients or salts. If you are unsure, start conservative, keep the base soil as the larger portion, and adjust over future seasons as you see how the bed drains and grows.
Formula used
The calculator multiplies bed length by width to get square feet, converts the fill height from inches to feet, and multiplies to get cubic feet per bed. It multiplies by the number of beds, adds the settling allowance, and divides by 27 for cubic yards. Bags are total cubic feet divided by the bag volume, rounded up.
The compost portion is the total cubic feet multiplied by the blend share, and the base soil portion is whatever is left. Both are shown in cubic feet so you can buy bags or bulk of each component to roughly match the blend.
Bagged versus bulk fill
For one or two small beds, bags of raised bed mix or separate bags of soil and compost are easy to handle. Once several beds are involved, the bag count climbs fast and bulk delivery of soil and compost usually becomes cheaper, as long as you have somewhere to dump the piles and time to move them.
The calculator shows cubic yards and a bag count together so the crossover point is clear. If you are comparing prices, include delivery fees, bag counts, and the labor of carrying material to the beds, not just the price per unit.
Common mistakes
The most common mistake is measuring the frame instead of the inside of the bed, which overstates the volume. Another is forgetting settling. Fresh soil and compost drop noticeably after the first few waterings, so a small allowance and a planned top-up are normal.
Filling a deep bed entirely with pure compost is also a frequent mistake. Compost is an amendment, not a complete growing medium, so most blends keep it as a portion of the mix and use base soil for the bulk and structure.
Quick reference
Soil needed by raised bed size (10 in fill, before settling)
| Bed size | Cubic feet | Cubic yards | 1.5 cu ft bags |
|---|---|---|---|
| 2 x 8 ft | 13.3 cu ft | 0.49 cu yd | 9 bags |
| 3 x 6 ft | 15 cu ft | 0.56 cu yd | 10 bags |
| 4 x 4 ft | 13.3 cu ft | 0.49 cu yd | 9 bags |
| 4 x 8 ft | 26.7 cu ft | 0.99 cu yd | 18 bags |
At 10 inches of fill before settling. Change the fill height in the calculator for deeper beds or partial fills.
FAQ
Raised Bed Soil Calculator FAQ
How do I calculate soil for a raised bed?
Multiply the inside length by width for square feet, multiply by the fill height in feet for cubic feet, then multiply by the number of beds. Divide by 27 for cubic yards and add a small settling allowance.
How much soil do I need for a 4x8 raised bed?
A 4 by 8 foot bed filled 10 inches deep needs about 26.7 cubic feet, or roughly 1 cubic yard, before settling. The calculator updates this as you change the height and number of beds.
How much compost should I mix into a raised bed?
A common planning range is about a quarter to a third compost with the rest base soil. The calculator defaults to a 30 percent compost share and shows the compost and base soil volumes separately.
Should I fill a raised bed with only compost?
Usually no. Compost is an amendment rather than a full growing medium. Most blends keep compost as a portion of the mix and use top soil or garden soil for the larger base.
How deep should a raised bed be?
Many vegetables grow well in 8 to 12 inches of good soil. Deeper beds can be filled partly with coarse material at the bottom, so enter the depth of quality mix you actually plan to add.
Is it cheaper to buy bagged or bulk soil for raised beds?
Bags are convenient for one or two beds, but bulk soil and compost are usually cheaper once several beds are involved. The calculator shows bags and cubic yards together so you can compare.
Methodology
Who built and reviewed this estimate
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