Mulch Calculator — Bags & Coverage
Calculate mulch needed in litres and bags for garden beds and borders.
Last updated: April 2026 · Source: RHS — Mulching
Volume
900 litres
50L Bags
18
100L Bags
9
Est. Cost
£90.00
Disclaimer
This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.
How It Works
Mulch volume is calculated as area × depth. The RHS recommends applying organic mulch (bark, wood chip, garden compost) to a depth of 50–75 mm (5–7.5 cm). This depth suppresses weeds, retains moisture and insulates roots without smothering the soil. For gravel mulch, 25–40 mm is usually sufficient.
This calculator shows volume in cubic metres, litres and the number of bags needed. Standard bags are 50–80 litres; bulk bags hold approximately 0.5–1.0 m³. Bark mulch weighs roughly 300–400 kg per m³ loose; composted material is heavier at 500–700 kg per m³.
Enter the bed area and desired depth. The calculator shows total volume, bags or bulk bags needed and estimated cost. Apply mulch in late spring after the soil has warmed, or in autumn. Keep mulch 5–10 cm away from plant stems and tree trunks to prevent rot.
Example: Border beds 18 m² total area, 75 mm bark mulch
- Volume: 18 × 0.075 = 1.35 m³ (1,350 litres)
- Bags (70 L each): 1,350 ÷ 70 = 19.3, round to 20 bags
- Or 2 bulk bags (0.7 m³ each)
- Estimated cost: £80–£120 (bags) or £60–£90 (bulk)
Source: RHS — Mulching
Frequently Asked Questions
- What does the Mulch Calculator — Bags & Coverage do?
- Calculate mulch needed in litres and bags for garden beds and borders. All calculations are performed in your browser using official UK rates and thresholds.
- Does this include delivery costs?
- This calculator estimates material quantities and approximate costs. Delivery charges vary by supplier, quantity and location. Bulk orders often qualify for free or reduced delivery.
- When is the best time for this project?
- Timing depends on the specific project. Generally, spring and autumn are ideal for lawn and planting work, while hard landscaping can be done year-round in dry conditions.