Weed Control Coverage Calculator
Calculate weed killer or pre-emergent herbicide needed for your lawn or garden from area size and product concentration.
Returns correct mix and total quantity.
Weed control product coverage calculates how much herbicide, pre-emergent granule, or mulch you need to treat a specific garden or lawn area, preventing under-application (ineffective) or over-application (plant damage, waste).
Core formula: Product Needed = Treatment Area ÷ Coverage Rate per Unit Treatment Area = Length × Width (in square feet or acres)
Unit conversions:
- 1 acre = 43,560 sq ft
- 1,000 sq ft = 0.023 acre
- Liquid rate: oz per gallon × gallons per 1,000 sq ft
Common weed control types and application rates:
Pre-emergent granules (prevents weed seeds from germinating):
| Product Type | Typical Rate |
|---|---|
| Corn gluten meal (organic) | 20 lbs per 1,000 sq ft |
| Pendimethalin granule | 2–3 lbs per 1,000 sq ft |
| Prodiamine (Barricade) | 1.5–2.3 lbs per 1,000 sq ft |
Liquid herbicides (post-emergent — kills existing weeds):
| Product | Dilution | Coverage |
|---|---|---|
| Glyphosate (Roundup) concentrate | 2.5 oz per gallon water | 300 sq ft per gallon mix |
| Vinegar solution (organic, 20% acetic acid) | Undiluted | 50–75 sq ft per liter |
Mulch (physical suppression): Depth needed: 2–3 inches for effective weed suppression Cubic feet of mulch = Area (sq ft) × Depth (ft)
Worked example: A 1,500 sq ft lawn needs pre-emergent treatment with pendimethalin at 2.5 lbs/1,000 sq ft. Product needed = (1,500 ÷ 1,000) × 2.5 = 3.75 lbs
A 200 sq ft garden bed needs 3-inch mulch coverage: Cubic feet = 200 × (3/12) = 50 cubic feet ≈ 1.85 cubic yards
Application timing: Pre-emergents must be applied before soil temperature reaches 55°F (13°C) at 2-inch depth — when forsythia blooms in spring is a reliable indicator. Post-emergents work best on actively growing weeds in warm weather.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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