Weed Killer Dilution Calculator Guide
Use this weed killer dilution calculator to measure herbicide concentrate for your sprayer. Enter the label application rate (oz per gallon or ml per liter) and sprayer volume to get the correct concentrate amount with automatic unit conversion.
How to use the weed killer dilution calculator
Enter the concentrate rate from your herbicide label, select oz/gallon or ml/liter, then enter sprayer volume in gallons or liters.
The calculator converts mixed units when needed and returns total concentrate in ounces or milliliters.
Herbicide dilution formula
When units match: Concentrate = Application rate × Sprayer volume. Cross-unit conversions use 1 gallon = 3.78541 liters before multiplying.
Example (matching units): 2 oz per gallon in a 3-gallon sprayer = 6 oz concentrate total.
- Concentrate = rate × sprayer volume (same units)
- Liters to gallons: divide by 3.78541
- Gallons to liters: multiply by 3.78541
- Never exceed label rate — illegal and phytotoxic
Worked example
Label rate is 2 oz of concentrate per gallon. You are filling a 1-gallon pump sprayer.
Concentrate needed = 2 × 1 = 2 oz. Add 2 oz concentrate to the tank, agitate, and fill to 1 gallon with water.
Selective vs non-selective herbicides
Non-selective herbicides (glyphosate, etc.) kill most green plants they contact — use precise spot spraying and avoid drift. Selective lawn herbicides target broadleaf weeds without killing grass but still require label-rate mixing.
Never mix different herbicide classes unless the label explicitly allows it.
Safety and environmental tips
Wear chemical-resistant gloves and avoid spraying on windy days. Keep children and pets off treated areas until sprays dry. Follow local regulations for aquatic buffers and application timing.
- Dedicated sprayer for herbicides only — never reuse for foliar feed.
- Clean equipment after each use to prevent residue damage.
- Spot-treat weeds instead of blanket spraying where possible.
- See spray mix calculator for general concentrate scaling.