GARDEN FIELD BOOK / CALCULATOR 06
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Raised Bed Soil Calculator
Measure the inside of your raised bed and choose the depth you will actually fill. Get soil volume in cubic feet, cubic yards and liters, plus a bag estimate based on the package you plan to buy.
12 in soil depth · one bed
16 bags × 2 ft³
YOUR MEASUREMENTS
Measure the space to fill
Use inside dimensions, not the outside of the wooden frame. Fill depth is the depth of new soil you need, not automatically the total wall height.
YOUR SOIL ESTIMATE
Volume and bag count
Measure once. Order with confidence.
Calculate to see the volume of soil that fits your beds and the quantity to purchase.
1 bed at 12 in fill depth
16 bags of 2 ft³; purchase allowance 0%
Measure only the inside depth you intend to fill with new soil. Leave space at the top when your planting and mulching plan requires it.
THE MATH
How to calculate raised bed soil volume
Use internal dimensions
Measure the clear length and width inside the walls. Measure the thickness of the new soil layer from its bottom to your planned fill line.
Convert to cubic feet
Multiply length × width × fill depth in matching units. For identical beds, multiply the result by the number of beds. Divide ft³ by 27 for yd³.
Round bags up
Divide your purchase volume by the amount printed on the bag, then round up to the next whole bag. Only add a purchase allowance if you select one.
For one 4 × 8 ft raised bed filled to 12 inches (1 ft), the required soil is 32 ft³, or about 1.185 yd³. With 2 ft³ bags and no extra allowance, that is 16 bags. These values describe the space to fill, not the weight of soil or a specific soil-mix recipe.
CHECK BEFORE ORDERING
What this estimate does and does not cover
A 12-inch-high frame does not necessarily mean 12 inches of new soil. If you reserve room for mulch or work existing soil into the base, measure only the new fill layer.
The same measured volume can be expressed as bags or cubic yards. Confirm your supplier’s actual bag size and bulk quantity before ordering.
The tool does not invent settling, compaction, soil density or mix proportions. An optional extra allowance affects purchase volume only.
References and Sources
Iowa State University Extension: Success With Your Vegetable Garden (2024). Includes the raised-bed length × width × depth calculation and the conversion from cubic feet to cubic yards.
Iowa State University Extension: Creating Raised Bed Planters. Discusses measuring bed fill and leaving room for top layers. The calculator uses the reader’s measurements, not a preset horticultural recommendation.