Soil Calculator for Raised Beds, Planters and Bed Prep
Enter your project dimensions
Raised beds are what bring most people to this page, and in this state they usually get built for a reason: the native ground is clay over shale that stays wet into May, and a box sitting on top of it drains when the ground below will not. The soil calculator sizes what goes into that box. What it cannot do is tell you how much of the volume the ground underneath will take back as the blend settles into it, which is why the number you order and the number that stays in the bed a month later are never quite the same.
What a bed volume leaves out about the ground beneath it
An open-bottomed bed on undisturbed clay is a container with a leaky floor. The first season, some of the blend works down into the loosened surface below it and the level in the box drops. A bed on a cleared, broken-up subsoil settles more than one set on sod. Neither is a fault in the arithmetic; both are a reason to order past the rim rather than level with it.
Before the soil goes in, break the top inch or two of ground inside the frame. Roots cross a gradual change between layers far more readily than a hard line between imported soil and sealed clay.
Three weights behind one soil calculator: 2,000, 2,200 and 2,400 lb
The tool works out the volume from your measurements, then applies the published weight of whatever you selected. Garden Soil, blended with compost, is the lightest at about 2,000 lb per cubic yard, which works out at an even 1.00 ton per yard. Top Soil, screened, runs near 2,200 lb, or 1.10. Fill Dirt is the heaviest at roughly 2,400 lb, or 1.20, and a soaked yard of it can reach 3,000. All three figures are approximate.
Soil is ordered by the cubic yard, so the yard figure is the one that matters most here. Tons are useful for picturing what is landing on the drive, and cubic feet converts straight into bags if you are comparing with what is left in the shed.
Adding three beds up in a single pass
Shapes first: rectangle, circle, or multiple areas, which holds five pieces and totals them. Length, width and diameter go in as feet, depth in inches between 0.25 and 24. Choose the blend from the material list, tick the optional five percent for compaction and spillage, and calculate. Email my quote sends the figure on.
Example only. Two beds at 4 by 10 ft and one planter at 3 by 6 ft, all filled to 12 inches with garden soil.
- Bed areas: 4 x 10 = 40 sq ft each, so 80 sq ft for the pair
- Planter: 3 x 6 = 18 sq ft
- Total area: 98 sq ft
- Volume at 12 inches: 98 x 1 ft = 98 cu ft
- Cubic yards: 98 divided by 27 = 3.63 yd3
- Tons at 1.00: 3.63 tons
- With the five percent ticked: 3.81 yd3
Measure the inside of the frames. The boards take a real bite out of the area, and across three beds that is a wheelbarrow or two.
An empty box takes a foot; tired ground takes two inches
Match the depth to what the soil is doing. An empty raised planter takes the full 12 inches. A new in-ground bed wants 6 inches worked into the native soil. Refreshing an established bed is 4 to 6 inches over the top. And where the ground is simply tired rather than unusable, mix 2 to 3 inches of garden soil through the top 6 inches instead of replacing anything: a 200 sq ft bed treated that way is 200 by 0.25 ft, which is 50 cu ft, or 1.85 yd3, against 3.70 yards if you replaced the top six inches outright.
A 30-inch bed does not need garden soil to the bottom
Tall beds are where orders get expensive for no return. Roots work the upper part of the box, so the bottom third can be fill dirt or coarse organic material that composts down in place, with 8 to 12 inches of blended soil above it. Run the two layers as separate calculations. A 4 by 12 ft bed 30 inches tall, with 18 inches of fill below and 12 inches of garden soil above, is 48 sq ft by 1.5 ft, or 72 cu ft, or 2.67 yd3 of fill dirt at about 3.2 tons, and 48 cu ft, or 1.78 yd3, of garden soil on top.
Ordering past the rim, because compost blends drop
Blended soils shrink as the compost in them breaks down, commonly 10 to 20 percent over the first weeks. That is more than the five percent tick box allows for, so fill the beds proud, water them heavily, and refill once rather than ordering a second small load later. Heavily planted beds usually want an inch or two added each spring regardless.
Time the delivery for a week you can move it. Soil that gets rained on before it is spread turns into a job with a shovel rather than a wheelbarrow, and it stains a concrete drive, so ask for it on a tarp if the tipping spot is paved.
Planting, lawn or lift: the page your order belongs on
Use this page for anything you are planting into: beds, planters, borders and bed prep, ordered as garden soil. Move to the topsoil calculator when the work is lawn, seedbed or finish grading, since screened topsoil is the material there and it carries its own depth guidance. Use the dirt calculator when the job is raising a grade, backfilling or filling a low spot, where fill dirt does the structural work and growing soil goes on last. Getting that split right is usually worth more than any allowance percentage.
Once the yardage is settled, open the product page for the blend you sized, set the quantity and the date there, and pick a firm, open tipping spot. Delivery is arranged at checkout by ZIP code. Bed layouts that will not break into rectangles can go through the contact page.
Common questions
The bed is terraced into a bank, so one end is deeper than the other. What depth do I enter?
Enter each level as its own area with its own depth rather than averaging them. Measure the depth from the soil surface you want down to the bottom of that section, at the middle of it. Averaging a terraced bed usually leaves the lower box short, which is the end that drains worst.
My bed wraps the corner of the patio in an L. Can the tool add that up?
Yes, in multiple areas. Split the L into two rectangles that do not overlap, running the long arm its full length and starting the short arm where the long one ends. Otherwise the corner goes in twice, which on a 12-inch bed is a real quarter yard.
Do I measure to the outside of the timber or the inside?
Inside, every time. The frame does not hold soil, and the boards take a real bite out of what looks like the bed area. The same goes for a stone or block edging around an in-ground bed.
I want fill in the bottom of a tall bed and good soil on top. How do I order both?
Run the tool twice and order two materials. Take the lower layer at its depth in fill dirt and the upper 8 to 12 inches in garden soil, then read the yards for each separately. They carry different weights per yard, so one combined figure would be wrong for both.
The border bed is a long curve, not a rectangle. How do I estimate it?
Lay the largest rectangles you can inside the curve and add a circle for a rounded end, then enter them as separate areas. Where a bed pinches in and out, measure its width at three or four points and use the average width with the full length, then round up.
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