Soil Amendment Calculator

Estimate how much soil amendment to add to a garden, raised bed, lawn area, flower bed, or planting area. Calculate compost, manure, peat moss, gypsum, lime, sulfur, organic matter, pounds, cubic feet, cubic yards, bags, and cost.

Calculate Soil Amendment

Amendment Volume = Area × Amendment Depth. Bags Needed = Total Volume ÷ Bag Size.
Your result will appear here.

How the soil amendment calculator works

Depth mode:
The calculator uses garden area and amendment depth to estimate cubic feet, cubic yards, pounds, bags, and cost.

Rate mode:
The calculator uses an application rate such as pounds per 100 square feet or cubic feet per 100 square feet.

pH mode:
The calculator gives a rough lime or sulfur estimate based on pH change, area, mixing depth, and soil texture.

Bag coverage mode:
The calculator estimates how many bags are needed based on the coverage listed on the bag.

Why use a soil amendment calculator?

A soil amendment calculator helps estimate how much material is needed before buying compost, lime, sulfur, gypsum, manure, peat moss, or other soil products.

It can help avoid buying too little, over-applying amendments, underestimating bag counts, or guessing costs for garden beds, lawns, and planting areas.

What your result means

Your result shows cubic feet, cubic yards, pounds, bags needed, cost, amendment depth, amendment percent by volume, area covered, and estimated material amount based on the selected calculation method.

Soil amendment formulas

Frequently asked questions

How do I calculate how much soil amendment I need?

Measure the area, choose an amendment depth or application rate, then calculate the volume or weight needed. Add extra material if the area is uneven or bags settle.

How much compost should I add to garden soil?

Many garden beds use a layer of compost measured by depth, such as 1 to 3 inches, then mix it into the top several inches of soil depending on the crop and soil condition.

How many cubic feet are in a cubic yard?

There are 27 cubic feet in 1 cubic yard.

Should I use lime or sulfur to change soil pH?

Lime is commonly used to raise acidic soil pH. Sulfur is commonly used to lower alkaline soil pH. Use a soil test before making major pH changes.

Is this soil amendment calculator exact?

No. This is an estimate. Actual soil amendment needs vary by soil test results, soil texture, organic matter, crop type, product strength, moisture, compaction, and local growing conditions.