Mulch Calculator
Mulch Calculator works out Area covered and Depth from Material, Density from your supplier and What you are starting from. The default figures on this page give volume of 4.6296 yd3; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
6 steps
- Area = 500 sq ft entered directly = 500 sq ft
- Depth = 3 in = 0.25 ft
- Volume = 500 x 0.25 = 125 cu ft = 4.6296 cu yd
- Density = 18.519 lb/ft3 (EPA table: Wood chips, shredded - 1 cubic yard - 500 lb (U.S. EPA); 500/27 = 18.519)
- Weight = 125 x 18.519 = 2314.8 lb = 1.157 US short tons
- Bags = ceil(125 cu ft / 2 cu ft) = 63
Figures from bulk material densities, checked 31 August 2026. Its 9 worked examples are re-run on every release, last on 15 September 2026. What changed · how reference data is kept current
Sources and references
4 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the Mulch Calculator calculates
Converts a covered area and spread depth - or a known tonnage, or a measured stockpile - into the volume of gravel, sand, topsoil, mulch, compost or decorative stone required, in cubic feet, cubic yards, cubic metres, bags, tons and tonnes, with a soil-blend split and cost by the yard, the ton or the bag.
How to use this Mulch Calculator
Enter Material, Density from your supplier, What you are starting from and Weight you have or are buying. Area covered updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Area covered, Depth and Volume.
The method follows U.S. EPA, Standard Volume-to-Weight Conversion Factors (loose bulk densities for gravel, sand, stone, soil, wood chips and compost), ASTM C29/C29M, Standard Test Method for Bulk Density (Unit Weight) and Voids in Aggregate, NIST Special Publication 811, Guide for the Use of the International System of Units (exact ft-to-m and lb-to-kg conversions) and Interlocking Concrete Pavement Institute, Tech Spec 2: Construction of Interlocking Concrete Pavements (1 in / 25 mm screeded bedding sand course).
What you can compare
Change one input at a time to see how it affects Area covered, Depth and Volume. The inputs you can vary are Material, Density from your supplier, What you are starting from, Weight you have or are buying, Shape of the pile and Base diameter / width of the pile.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How can I calculate how much mulch I need?
Converts a covered area and spread depth - or a known tonnage, or a measured stockpile - into the volume of gravel, sand, topsoil, mulch, compost or decorative stone required, in cubic feet, cubic yards, cubic metres. Open “How this is worked out” beside the result to see each step for your own figures.
What is the 3-3-3 rule for mulch?
On the figures this page opens with — length 20, width 10, depth of the layer 4 and extra for compaction, settlement and spillage 0% — the volume is 4.6296 yd3. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
How much do 20 bags of mulch cover?
It needs Material, Density from your supplier, What you are starting from, Weight you have or are buying, Shape of the pile and Base diameter / width of the pile. Nothing else is required, and the figures stay in your browser.
How many 2 ft 3 bags of mulch equal 1 yard of mulch?
The result gives Area covered, Depth, Volume, Order this much (rounded up to the half yard), Bulk density used and Weight, each labelled with its unit so the figure can be read on its own.
What information do I need for the Mulch Calculator?
You need Material, Density from your supplier, What you are starting from, Weight you have or are buying, Shape of the pile, Base diameter / width of the pile, Height of the pile and Length of the straight ridge (windrow only). The page opens with default figures that give volume of 4.6296 yd3, so you can see the scale before entering your own.
What does this Mulch Calculator show?
It shows Area covered, Depth, Volume, Order this much (rounded up to the half yard), Bulk density used, Weight, Bags needed and Order this much (rounded up to the half ton), with the working and any warnings for your entries.