MEASURE & FILL
Measure a raised bed for soil without buying by the frame size
Use inside dimensions and the soil depth you actually need. A worked example shows how to combine different beds into one clear order.
Start inside the walls
A timber or metal frame can add several inches around the planting space. For a rectangular bed, measure the inside length and inside width where the soil will sit. Use those dimensions in the calculator rather than the size printed on a kit box or the outside edge of the frame.
For fill depth, measure only the soil you still intend to add. A 12-inch-tall new frame does not always need 12 inches of new material, and an established bed may need only a shallow top-up. Write the planned fill depth beside each bed before opening a supplier quote.
Keep different beds separate until the total
List each shape and its own missing depth. Beds with the same dimensions and the same fill depth can use the identical-beds quantity field. A bed with a different depth should be a separate entry, even when it has the same footprint. This makes the printed plan easier to check against the garden.
The calculator totals every entry before it rounds the purchase quantity. That is useful when one order can serve all the beds. If you must buy or deliver soil separately for each bed, calculate each order separately because whole-bag rounding can change the result.
A three-bed worked example
Suppose you are filling one 6 × 3-foot bed by 8 inches, topping up one 4 × 8-foot bed by 4 inches, and filling two identical 2 × 6-foot beds by 6 inches. These are inside dimensions and planned fill depths.
The three entries need 12, 10.667 and 12 cubic feet respectively, for a combined measured total of 34.667 cubic feet. With 2-cubic-foot bags and no allowance, the combined order rounds to 18 bags, supplying 36 cubic feet. The 1.333 cubic feet above the measured total comes from whole-bag rounding.
(6 × 3 × 8 ÷ 12) + (4 × 8 × 4 ÷ 12) + (2 × 6 × 6 ÷ 12 × 2) = 34.667 cubic feet
| Bed entry | Measured volume | 2 cu ft bags if ordered alone |
|---|---|---|
| 6 × 3 ft, 8 in fill | 12 cu ft | 6 |
| 4 × 8 ft, 4 in top-up | 10.667 cu ft | 6 |
| Two 2 × 6 ft beds, 6 in fill | 12 cu ft | 6 |
| One combined order | 34.667 cu ft | 18 |
Use an average only for a genuinely uneven top-up
If the existing soil surface is uneven, check the missing depth at several representative points and use a stated average only when the bed is otherwise a simple rectangle. For example, four missing-depth readings of 2, 3, 4 and 3 inches have an average of 3 inches. Record the readings so you can revisit the choice before ordering.
An average is a planning estimate, not a prediction of future settling. Do not quietly add a second allowance because a result feels uncertain. If you want extra material for your own reason, enter one explicit purchase allowance and keep it visible in the plan.
Finish with a buying checklist
Before placing an order, compare the printed entries with the garden: inside dimensions, fill depth, number of identical beds, bag volume or bulk increment, and delivery limits. Check the product label and quote separately; this calculator measures space and does not establish that two products are equivalent.
For a circular bed, use the inside diameter. For an irregular bed, divide the fill area into rectangles or other simple sections you can measure, then add entries. A rough outside-frame measurement is less useful than a transparent set of smaller measurements.