Weed Control & Herbicide Dosage Calculator
Calculate the exact amount of herbicide product needed for your field, accounting for area size, recommended active ingredient rate, and product concentration.
Formulas Used
1. Total Active Ingredient (AI) Needed:
Total AI (oz) = AI Rate (oz AI/acre) × Area (acres)
2. AI per Gallon of Product:
AI per gal product (oz AI/gal) = (% AI ÷ 100) × Product Density (lb/gal) × 16 (oz/lb)
3. Product Volume Needed:
Product (gal) = Total AI (oz) ÷ AI per gal product (oz AI/gal)
4. Total Carrier Water:
Water (gal) = Water Rate (gal/acre) × Area (acres)
5. Total Spray Volume:
Total Spray (gal) = Product (gal) + Water (gal)
6. Mixing Ratio:
Product per 100 gal water = (Product gal ÷ Water gal) × 100
Area Conversions:
1 hectare = 2.47105 acres | 1 acre = 43,560 ft² = 4,046.856 m²
Assumptions & References
- The AI rate (oz AI/acre) must be taken directly from the herbicide product label for the target weed species and crop.
- Default product density of 8.34 lb/gal is used for water-based liquid formulations (density of water). Oil-based or emulsifiable concentrates may differ (typically 8.0–9.5 lb/gal).
- Carrier water volume of 10–40 gal/acre is typical for ground boom sprayers; aerial application typically uses 2–5 gal/acre.
- This calculator applies to liquid herbicide formulations (EC, SL, SC, EW). Dry formulations (WP, WDG, DF) require weight-based calculations.
- Results assume uniform application across the entire field area with no overlap or buffer zones.
- Always calibrate your sprayer before application to verify actual output matches the target rate.
- References: USDA NRCS Pest Management, EPA Label Requirements (40 CFR Part 156), Cooperative Extension Herbicide Guides (e.g., Purdue, Penn State, UC Davis).
- Legal notice: Always comply with federal, state, and local pesticide regulations. The herbicide label is a legal document — it is a violation of federal law to use a pesticide inconsistent with its labeling (FIFRA, 7 U.S.C. §136).