Stop guessing compost bags before weekend planting projects. Adjust depth, bag volume, and budget instantly. Print results, save records, and buy exactly enough today.
| Scenario | Bed size | Depth | Bag size | Settling + waste | Estimated bags |
|---|---|---|---|---|---|
| Vegetable bed refresh | 8 ft × 4 ft | 2 in | 40 L | 1.10× + 5% | 3 |
| Flower border top-dress | 12 ft × 3 ft | 1.5 in | 1.5 cu ft | 1.08× + 5% | 3 |
| Round tree ring | 6 ft diameter | 2 in | 25 L | 1.15× + 8% | 7 |
Compost is usually applied as a layer rather than mixed deeply. For vegetable beds, 1 to 2 inches is common for seasonal refreshes, while 2 to 3 inches suits heavy feeders and new beds with low organic matter. Lawn top-dressing often uses 0.25 to 0.5 inch so grass blades remain visible. This calculator converts depth into volume so you can order bags confidently.
Bag labels may be listed in liters or cubic feet. A 40 L bag equals about 1.41 cu ft, while a 25 L bag is about 0.88 cu ft. Loose, fluffy compost also compresses during transport and spreading. Using a settling factor of 1.08 to 1.15 helps match real yield, especially when the product is very dry or heavily screened.
Even careful spreading creates small losses: compost sticks to tools, drops between boards, or ends up in paths. A 3% to 8% waste allowance is practical for most gardens. Raised beds with tight borders can stay near 3% to 5%. Irregular borders, mulch rings, and windy conditions tend to push waste closer to 8%.
Rectangles fit standard beds and borders. Circles work well for tree rings, round planters, or circular beds. If your area is complex, estimate the total coverage area and use the custom volume mode from a prior measurement, or split the project into smaller rectangles and circles. The history table and export buttons help track multiple zones.
When price per bag is entered, the result includes an estimated total cost so you can compare bagged compost to bulk deliveries. For large jobs, rounding up reduces the risk of stopping mid-application. If storage space is limited, calculate zones separately and purchase in batches, keeping moisture protected to preserve microbial activity. For container gardens, aim for 10% to 20% compost by volume when lightly blending, not as a layer.
Most beds use 1–2 inches for a seasonal refresh. Use 2–3 inches when soil is depleted or you are building organic matter quickly. Lawns typically use 0.25–0.5 inch to avoid smothering grass.
Bagged compost can compress and you will lose some material to handling and uneven edges. Settling accounts for compaction; waste covers spills and leftover bits. Together they reduce under-ordering.
Round up when the job must be finished in one session, or when delivery time is uncertain. Nearest is fine for small projects where you can easily buy one more bag later.
Divide the space into simple rectangles and circles, then add the results. Alternatively, measure total area in square feet or square meters and use the custom volume option if you already know the required volume.
Larger bags often reduce cost per liter, but availability varies. Compare by converting to liters or cubic feet, then divide price by volume. The calculator helps by using a consistent unit for bag volume.
Yes. Enter the same bed dimensions and target depth, then set a settling factor that matches the material. Mulch usually settles more than compost, while potting mixes can vary widely by moisture and particle size.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.