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.