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Mulch calculator

Estimate top-up mulch by shape and depth, then compare complete bags with bulk orders and entered delivery charges. Review the method, a worked example and the limits before using your result.

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GARDEN PLANNING · MULCH ESTIMATOR

Mulch calculator

Plan new beds or a top-up. Compare whole bags with bulk mulch using your prices.

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Mulch project inputs
1Beds & tree rings

Enter non-overlapping beds. Target depth is the total layer you want; retained mulch is the usable layer already there. Only the missing depth is ordered.

Use separate rectangles for an L-shape. Different beds may have different depths; all share one mulch product. Positions between beds are not inferred.

2Order quantities

Editable allowance for handling or uneven spreading. No automatic settling factor.

Choose the volume printed on your bag. No bag size is assumed; bulk calculation works without one.

0 = exact volume. Otherwise round up to your supplier’s order increment, e.g. 0.25 yd³.

3 · Compare prices (optional)

One charge for the whole order. Enter 0 if none.

One charge for the whole order. Enter 0 if none.

Blank means unknown; 0 means free. Currency changes the label, not an exchange rate. Enter current quotes; no prices are assumed.

How to use

  1. Add rectangles, circles or rings. Enter a target total layer depth and the existing usable mulch depth for each zone.
  2. For a ring, specify the complete unmulched central diameter. For rectangular exclusions, enter their positions and dimensions.
  3. Enter the product’s bag volume or a bulk order increment, plus your chosen allowance. Add prices and optional delivery or collection charges.
  4. Compare required new volume, bag and bulk purchases, and complete known totals rather than material prices alone.

Calculation method

New depth is the target depth minus the entered existing layer, with no negative top-up. Each zone’s area and quantity multiply that new depth. Rectangle exclusions and a ring’s central area are deducted in their supported geometry. Apply the allowance to total new volume, then round bag count or a nonzero bulk increment. A selected delivery or collection charge applies once to a positive order. A blank charge remains unknown, while zero is an explicitly free charge.

Worked example

A 4 × 3 m rectangle with a 75 mm target layer and no existing mulch needs 0.9 m³. A 5% allowance gives 0.945 m³. Nineteen 50 L bags supply 0.95 m³; a 0.25 m³ bulk increment supplies 1 m³. At 5 USD per bag versus 60 USD/m³, materials cost 95 and 60 USD respectively. A 50 USD bulk delivery fee changes the second total to 110 USD.

Assumptions and limits

Depth and allowance examples are not planting recommendations. The central exclusion of a ring represents all space that will remain unmulched, not just a tree trunk. Separate zones do not establish their positions relative to each other. The tool does not predict settling, moisture change, decomposition or suitability of a mulch product.

Continue your plan

Use the topsoil calculator for fill beneath the mulch, the area calculator for measurements, and the gravel calculator for a separate mineral covering.

Copy, download or print a valid result to keep the inputs with the estimate. Currency selections label your prices; they do not apply an exchange rate. Product-dependent examples should be replaced with data for the material or equipment you actually use.

For the measurement and planning details, read estimating mulch top-ups and comparing delivered costs.