Mulch Coverage Calculator

How much mulch do I need?

The basic formula: length × width × depth ÷ 27 = cubic yards. One cubic yard covers 100 sq ft at 3 inches deep, or 162 sq ft at 2 inches. A 2 cubic foot bag covers about 8 sq ft at 3 inches. This calculator does the math and accounts for irregular bed shapes.

Mulch depth depends on use

• 1 inch: Decorative only — won't suppress weeds.
• 2-3 inches: Standard for established beds. Suppresses most weeds, retains moisture.
• 3-4 inches: Around trees and shrubs, but keep mulch 2-3" away from trunks ("mulch volcanoes" rot bark).
• Past 4 inches: Counterproductive. Holds too much moisture, attracts pests, blocks air to roots.

Bark vs wood chips vs straw vs rubber

• Shredded hardwood bark: Best all-rounder. Holds in place, breaks down to enrich soil over 2-3 years. Lasts 1-2 seasons. ~$3-5/2 cu ft bag.
• Cedar/cypress chips: Pest-repellent (natural oils), pleasant smell. Lasts 2-3 years. ~$5-8/2 cu ft bag.
• Pine straw: Lightweight, acidifies soil — great for azaleas, blueberries, rhododendrons. Wash-away on slopes. ~$5/bale.
• Black-dyed mulch: Aesthetic, fades to gray-brown in 6 months. The dye is plant-safe but stains driveways.
• Rubber mulch: Lasts 10+ years, doesn't break down, but heats up significantly in sun. Best for playgrounds, not garden beds (no nutrient return).
• Stone/gravel: Permanent. No nutrients, doesn't suppress weeds long-term as roots find their way through.

When to apply mulch

• Spring (after soil warms, typically May): Standard refresh. Applying too early in cold/wet soil delays warming and root growth.
• Fall (after first frost): Insulates perennials and shrubs through winter freezes.
• Avoid mid-summer: If you must, water deeply first — dry mulch can wick moisture FROM the soil it covers.

How to apply mulch correctly

• Pull weeds first. Mulch slows weeds but doesn't kill what's already growing.
• Edge the bed — a clean edge of 4-6" deep makes mulch look intentional and prevents grass invasion.
• Water before AND after mulching. Especially in dry climates.
• Don't pile against trunks. "Mulch donuts" — 2-3" gap around trunk — are correct. Volcanoes invite rodents and rot.

How often to refresh

• Shredded bark: Top off every spring with 1" — full refresh every 2-3 years.
• Cedar/cypress: Top off every 2 years.
• Pine straw: Top off twice a year — it compresses fast.
• Stone: Once. Add fabric beneath to suppress weeds permanently.

Buying bag vs bulk

Bags are convenient but expensive: $3-5 per 2 cu ft bag = $40-67 per cubic yard. Bulk mulch from a local landscape supply runs $25-40 per cubic yard delivered. Buy bulk if you need more than 4 cubic yards — the delivery fee amortizes. Below that, bags save the hassle of shoveling from a driveway pile.