Inputs
Example Data Table
| Bed count | Shape | Dimensions | Allowances | Recipe | Total (ft3) | Total (yd3) |
|---|---|---|---|---|---|---|
| 2 | Rectangular | 4 ft × 2 ft × 0.5 ft | 10% settle, 0% extra | Equal thirds | 8.80 | 0.326 |
| 1 | Rectangular | 8 ft × 4 ft × 1 ft | 10% settle, 5% extra | Topsoil + compost | 36.96 | 1.369 |
| 1 | Circular | Diameter 1.2 m × depth 30 cm | 8% settle, 0% extra | Custom | 9.40 | 0.348 |
Formula Used
- Rectangular bed volume: V = L × W × D
- Circular bed volume: V = π × (d/2)² × D
- Total for multiple beds: Vbase = V × n
- Allowances: Vfinal = Vbase × (1 + s/100) × (1 + e/100)
- Component split: Vi = Vfinal × (pi/100)
- Bag count: Bags = ceil(Vi / bagSize)
How to Use This Calculator
- Choose the bed count and shape.
- Select your units, then enter length, width, and depth.
- Set settlement and extra allowances for real-world fill needs.
- Pick a recipe or enter custom percentages for A/B/C components.
- Enter bag sizes (ft3) and optional bag costs.
- Click Calculate Mix. The results appear above the form.
- Use Download CSV or Download PDF to save your report.
Raised Bed Mix Planning Notes
1) Measure volume before buying materials
Raised beds look small, but volume grows quickly with depth. A single 4 ft × 2 ft bed filled to 6 in needs about 4.0 ft3 of mix. Two beds need roughly 8.0 ft3 before allowances. This calculator converts the final requirement into ft3, yd3, and liters for easier purchasing.
2) Depth choices affect roots and water storage
Leafy greens often perform well around 6–8 in, while many vegetables benefit from 10–12 in. Deep beds hold more moisture and buffer temperature swings, but they require more mix. If you change depth from 6 in to 12 in, total volume doubles, so depth is the most powerful lever in your plan.
3) Add settlement and extra allowance for reality
Fresh mixes settle after watering and rain. A 5–15% settlement allowance is common, especially when using light organic components. Extra allowance covers uneven corners, spill losses, and topping up after the first week. The final volume is computed as Vfinal = Vbase × (1 + s/100) × (1 + e/100).
4) Use balanced recipes to manage drainage and fertility
Equal-part blends distribute nutrients and structure. Compost increases fertility; coir or peat improves moisture retention; airy components help porosity and oxygen. A topsoil and compost recipe can be economical for large beds, but confirm drainage and avoid compacted soil. Custom ratios let you adapt to climate and crop type.
5) Convert volume into bags and cost estimates
Retail products are sold by bag volume, commonly 1–3 ft3. Bag counts are rounded up to ensure you do not run short. If you enter a bag price, the tool multiplies it by the rounded bag count to estimate cost per component and a total. Compare yd3 totals with bulk delivery to evaluate savings.
FAQs
1) Which unit should I use for my bed dimensions?
Use the unit you measured with. The calculator converts everything internally and reports totals in ft3, yd3, and liters, so you can compare bagged products and bulk deliveries without manual conversions.
2) Why does the tool ask for settlement allowance?
Organic mixes compress after watering, rainfall, and foot traffic near edges. Settlement allowance reduces the chance of low spots and helps you fill the bed to your target depth from day one.
3) What is a good extra or waste percentage?
For clean builds, 0–5% is often enough. Use 5–10% if bed walls are uneven, you expect spills, or you plan to top-dress shortly after planting.
4) How does the circular bed option work?
Select circular shape and enter the diameter as the length value. Depth is the same input. Width is ignored for circular beds to keep the form consistent across shapes.
5) Can I use fewer than three components in a custom mix?
Yes. Set an unused component percent to 0. The calculator normalizes the remaining values to 100%, then computes volumes, bags, and optional cost for the active components.
6) Why are bag counts rounded up?
Store bags cannot be purchased in fractions. Rounding up ensures you have enough mix to reach full depth after settlement. Any small remainder can be saved for later topping or containers.
7) Should I choose bags or bulk delivery?
If your total is near or above 1 yd3, bulk can be cheaper and faster. For small totals, bags offer convenience and consistent quality. Use the cost fields to compare scenarios.