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Formula Used
| Bed shape | Area formula | Volume formula |
|---|---|---|
| Rectangle | Length × width | Area × fill depth |
| Circle | π × radius² | Area × fill depth |
| Oval | π × semi-major axis × semi-minor axis | Area × fill depth |
| Triangle | ½ × base × height | Area × fill depth |
| L-shape | Outer area − cut-out area | Area × fill depth |
| Custom sections | Sum of section areas | Total area × fill depth |
How to Use
- Select the closest garden bed shape.
- Enter dimensions using one consistent unit.
- Choose uniform or uneven soil depth.
- Deduct existing usable soil when necessary.
- Add waste and compaction allowances.
- Set mixture, bag, cost, and delivery details.
- Submit the form and review every estimate.
Example Data
| Example | Shape | Dimensions | Depth | Suggested allowance |
|---|---|---|---|---|
| Small herb bed | Rectangle | 4 ft × 2 ft | 8 in | 10% |
| Raised vegetable bed | Rectangle | 8 ft × 4 ft | 12 in | 15% |
| Round flower bed | Circle | 6 ft diameter | 10 in | 10% |
| Corner garden | L-shape | 8 ft × 6 ft outer | 12 in | 15% |
Recommended Soil Depths
Leafy greens often need six to eight inches. Root crops usually require deeper, loose growing material. Always check the mature root depth for each crop.
| Planting type | Typical depth |
|---|---|
| Shallow herbs and lettuce | 6–8 inches |
| Most vegetables | 10–12 inches |
| Root vegetables | 12–18 inches |
| Deep-rooted plants | 18–24 inches |
Frequently Asked Questions
Why add extra soil?
Loose soil settles after watering and normal use. Small handling losses also occur during filling. An allowance reduces the risk of ordering too little.
Should I use internal dimensions?
Internal dimensions represent the actual fillable space. External dimensions include the garden bed walls. Enter wall thickness when only external sizes are known.
How is uneven depth calculated?
The calculator averages minimum and maximum depths. This approach works for gently sloped bed bottoms. Highly irregular beds should use separate custom sections.
How are soil bags rounded?
The exact quantity may include a partial bag. Purchases are rounded upward to whole bags. Leftover volume shows the estimated unused material afterward.
Can I compare bagged and bulk soil?
Yes, both cost methods are calculated separately. Delivery and tax apply to each estimate. Local supplier minimums may change the final purchase price.
What density should I enter?
Use your supplier's material density when available. Moisture content can change soil weight considerably. The default value is only a practical estimate.
Do mixture percentages affect total volume?
The percentages divide the adjusted required volume. They must total exactly one hundred percent. Each component then receives its proportional quantity.
Can mulch be included?
Yes, assign part of the mixture to mulch. For surface-only mulch, calculate it separately instead. Use the mulch layer depth as the fill depth.
How accurate are the results?
Accuracy depends on measurements and realistic allowances. Soil compresses differently between products and moisture levels. Confirm large purchases with your material supplier.