Mulch and Soil Calculator Guide

What This Calculator Does

Estimate mulch, soil or topsoil volume from region areas and layer depths. The calculator combines up to 10 regions, reports ft³, yd³ and m³, rounds up whole bags and compares optional bagged and bulk material costs. Material choice identifies your task without assuming density or recommended depth.

When to Use It

Use it for garden beds, uniform layers and rectangular or circular footprints. Different regions can have different depths. For irregular boundaries, use square footage to measure net area, then choose Known area. For aggregate purchased by weight see gravel.

Inputs Explained

Rectangles need length and width; circles use diameter; known-area mode accepts total area. US mode uses ft, ft² and in depth. Metric mode uses m, m² and cm depth. Bag volume can be ft³, litres or m³. Allowance is 0–100%. Prices and bulk density are optional. Density always uses kg/m³, even with US dimensions.

How the Calculation Works

Region volume = area×depth. Rectangle area = length×width; circle area = π×(diameter/2)². Adjusted volume = sum of regions×(1+allowance/100). Whole bags = ceiling(adjusted volume/bag volume). Bag cost = whole bags×bag price. Bulk cost uses unrounded volume priced per yd³ in US mode or per m³ in metric. Metric tonnes = volume in m³×entered density/1000.

Example

For 100 ft² at 3 in deep, depth is 0.25 ft and volume is 25 ft³, approximately 0.925926 yd³ or 0.707921 m³. With 2 ft³ bags and no allowance, 25/2=12.5, so buy 13 bags. At an illustrative price of 4 per bag the material cost is 52. Bulk at an example 50 per yd³ costs about 46.2963. Delivery may change the real comparison.

How to Understand the Result

Adjusted volume includes allowance. Purchased bag volume includes the excess from whole-bag rounding. Density changes estimated weight but not volume or bag count. Each region’s area×depth breakdown uses metres consistently. Switching measurement systems converts valid dimensions and bulk-price basis, while the bag-volume unit stays independently selected.

Common Mistakes

Do not use bag mass as bag volume or confuse cubic yards with tonnes. Wet soil, dry soil and mulch need their own density data. Allowance is not a compaction or settling model. Plan soil blends, plant requirements and existing fill separately before entering your net required depth.

FAQ

Do mulch and soil use different equations?

The geometry is the same. Verify depth, packaging and density for each material.

Can it show tonnes?

Yes, only after you supply the actual bulk density.

Do prices include delivery?

No. The comparison covers material quantity multiplied by your entered price.

Notes

Active dimensions must be positive and at most 1e12; each region volume must be 1e−12 to 1e12 m³, total at most 1e12 m³, and whole bags at most 1e9. Derived costs and tonnes are limited to 1e15. Results use floating-point arithmetic, with up to six displayed decimals and two for costs. No planting prescription, density database, currency exchange or compaction model is included. Inputs are not persisted. For mixed concrete yield use concrete.