Calculator
Example Data Table
| Pan Type | Example Size | Approx. Volume (L) |
|---|---|---|
| Round | 23 cm diameter × 3.5 cm deep | 1.454 |
| Round | 9 in diameter × 1.5 in deep | 1.564 |
| Rect | 20 cm × 20 cm × 4 cm | 1.600 |
| Rect | 8 in × 8 in × 2 in | 2.098 |
Use these examples to sanity-check your measurements before mixing soil or compost.
Formula Used
- Round pan: V = π × (d/2)² × depth
- Rectangular pan: V = length × width × depth
- Unit conversion: 1 in³ = 16.387064 cm³, 1,000 cm³ = 1 L
- Gardening conversion: 1 ft³ = 28.316846592 L
How to Use This Calculator
- Select the pan shape that matches your container.
- Measure inside dimensions to the fill line.
- Choose centimeters or inches, then enter values.
- Set headroom for mixing soil and watering.
- Calculate, then use liters or cubic feet for recipes.
Practical Notes for Garden Use
Why pie-pan volume matters for potting mixes
Accurate volume helps you batch soil blends consistently across seed trays, pots, and plug cells. If a recipe calls for a 3:1:1 mix, knowing the pan’s liters lets you scale ingredients without guessing. Consistent ratios improve drainage, nutrient availability, and early root development. A small mismatch repeated across many batches can noticeably change moisture behavior and germination outcomes.
Measuring for real-world fill height
Measure inside dimensions to the practical fill line, not the top rim. Many pie pans flare, so the diameter near the base may be smaller than the rim diameter. For round pans, measure the inside diameter at the level you plan to fill. For rectangular pans, use inside length and width. Enter depth as the average depth you will actually fill.
Headroom and mixing space
Headroom prevents spills when you fold in compost, perlite, or slow-release amendments. The calculator includes a headroom percentage, which estimates a usable volume below total capacity. A 10% headroom setting is common for light mixing, while 20% is safer for vigorous blending or when you expect the mix to fluff.
Unit conversions for common garden recipes
Liters work well for precise blending, while cubic feet align with bagged potting media. The output also provides US quarts and gallons, which can match measuring jugs. For example, if you need 2 ft³ of mix, converting your pan’s usable liters to ft³ helps you count how many pan loads are required with minimal rounding error.
Planning propagation and top-dressing
Use the result to forecast how much medium you need per session. If your tray needs 6 liters and your pan yields 1.2 usable liters, plan five loads and a small remainder. For top-dressing, smaller measured batches reduce waste and keep amendments evenly distributed across containers. Accurate batching also supports repeatable trials when comparing fertilizers or moisture-retention additives.
FAQs
1) Should I measure the rim diameter or the inside diameter?
Use the inside diameter at your intended fill height. Rim measurements often overstate capacity because many pans taper inward. Inside measurements give a closer match to real soil volume.
2) My pan is sloped. Will the result still be useful?
Yes, as an estimate. For tapered pans, measure at the average fill height. If precision matters, take two diameters (top and bottom) and use the average diameter for a practical approximation.
3) What headroom percentage should I choose?
Start with 10% for gentle mixing and leveling. Use 15–25% if you will stir vigorously, add bulky perlite, or expect the mix to fluff and expand after hydration.
4) Can I use this for compost tea or liquid fertilizers?
You can, but liquid volumes are usually measured directly in liters or gallons. This tool is best for estimating container capacity when the vessel has an unusual shape or you lack markings.
5) Why does the calculator show both liters and cubic feet?
Liters support accurate recipe scaling, while cubic feet match typical bag sizes for potting media. Seeing both makes it easier to plan purchases and measure batches with less conversion work.
6) How can I validate the computed volume?
Fill the pan with water using a known measuring jug, then compare totals. This quick test also reveals how much taper or curvature affects the effective capacity at your chosen fill line.