Mulch Calculator
The Mulch Calculator computes the exact volume of mulch for rectangular, circular, or irregular garden beds. It estimates weight for 8 mulch types, calculates bags needed, provides cost estimates, and includes an interactive SVG bed diagram — features an AI chatbot cannot replicate. Free, no sign-up required.
Quick Presets
Bed Dimensions
Bed Shape
Unit System
Results
Bags Needed
4
bags
Area
32
sq ft
Area
2.97
m²
cu ft
8
cu ft
cu yd
0.3
cu yd
m³
0.227
m³
L
226.5
L
Weight
200
lbs
Weight
91
kg
Refresh Interval
12
months
Total Cost
$18.00
Cost per sq ft
$0.56
Bed Visualization
Coverage Reference
| Depth | Coverage per cu yd |
|---|---|
| 1" | 324 sq ft / cu yd |
| 2" | 162 sq ft / cu yd |
| 3" | 108 sq ft / cu yd |
| 4" | 81 sq ft / cu yd |
| 5" | 64.8 sq ft / cu yd |
| 6" | 54 sq ft / cu yd |
Mulch Types
| Type | Density (lbs/cu ft) | Refresh Interval |
|---|---|---|
| Hardwood | 25 lbs/cu ft | 12 months |
| Cedar | 20 lbs/cu ft | 18 months |
| Cypress | 22 lbs/cu ft | 18 months |
| Pine Bark | 18 lbs/cu ft | 10 months |
| Rubber | 45 lbs/cu ft | 60 months |
| Straw | 8 lbs/cu ft | 6 months |
| Gravel | 95 lbs/cu ft | Permanent |
| Cocoa Shell | 28 lbs/cu ft | 12 months |
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What is a Mulch Calculator?
A mulch calculator determines the exact volume of mulch needed to cover a garden bed at a specified depth. It converts bed dimensions into cubic feet, cubic yards, and metric units, then estimates the number of bags required and the total cost. Proper mulch coverage (2–4 inches for most gardens) suppresses weeds, retains soil moisture, regulates temperature, and improves curb appeal.
How to Use This Calculator
- Select the bed shape: rectangular, circular, or enter an irregular area directly
- Choose your unit system: imperial (feet/inches) or metric (meters/cm)
- Enter the bed dimensions (length × width, diameter, or total area)
- Set the desired mulch depth (2–3 inches for weed suppression, 4–6 inches for playgrounds)
- Select the mulch type to get an accurate weight estimate
- Optionally enter bag size and price to calculate cost
Frequently Asked Questions
How deep should I spread mulch in my garden?
For most garden beds, 2–3 inches of mulch is ideal. This depth suppresses weeds while allowing water to penetrate. Around trees, keep mulch 3–4 inches away from the trunk. For playgrounds, safety standards recommend 6 inches of wood mulch or 3 inches of rubber mulch.
How many bags of mulch do I need for a 4×8 raised bed?
A 4×8 ft bed at 3 inches deep needs about 8 cubic feet of mulch. With standard 2 cu ft bags, you need 4 bags. At $4–5 per bag, that is $16–20. For bulk delivery, that equals about 0.30 cubic yards.
What is the best type of mulch for vegetable gardens?
Straw and shredded hardwood are popular for vegetable gardens. Straw is lightweight, inexpensive, and decomposes to add organic matter. Hardwood mulch lasts longer (12 months) and provides better weed suppression. Avoid rubber mulch and dyed mulch in edible gardens.
How often should I replace mulch?
Replacement frequency depends on the mulch type: straw every 6 months, pine bark every 10 months, hardwood and cocoa shell every 12 months, cedar and cypress every 18 months. Rubber mulch can last 5+ years. Top up when the layer thins below 2 inches.