Herbicide Mix Calculator
Mix sprayer batches from area, coverage, and label rate.
What it does
Spray math punishes guessing twice: weak mixes waste the day and breed resistance, while hot mixes burn the lawn and break the law. Labels state rates per gallon and coverage per area; the only job left is clean division scaled to your ground.
The tool above does that scaling. Enter area, coverage, and product rate in imperial or metric to get spray volume, product amount, and a kitchen measure. Defaults treat 5000 ft2 at 1000 ft2 per gallon with 2 oz per gallon, so the page opens solved at 5 gal, 10 fl oz, and 20 tbsp.
The metric mirror lands together: 464.5 m2 at 24.5 m2 per L gives 19 L, and 15.6 mL per L gives 295.8 mL (about 0.3 L). Halving ground halves all three outputs, as the 2500 ft2 practice shows with 2.5 gal, 5 fl oz, and 10 tbsp. Doubling to 10000 ft2 doubles to 10 gal and 20 fl oz.
Labels outrank calculators every time. Rates, rain windows, temperature caps, protective gear, reentry times, and buffer zones come from the jug, not from this page. Drift turns small errors into neighbor problems, so spray calm air at low pressure with shields near beds and water.
Use the table for common lawn sizes at the example rate, then run your ground with your label numbers. The page mixes arithmetic only; it never approves a product, a rate, or a target. Within range it answers the shed question fast: how much water, how much product, and how many spoons.
How to use
- Pick imperial or metric.
- Enter the treatment area.
- Enter coverage per spray unit.
- Enter product rate per unit.
- Read spray volume first.
- Read product plus kitchen measure.
Formula
- Area
- Ground to treat.
- Coverage
- Ground covered per spray unit.
- Rate
- Product per spray unit.
Imperial divides ft2 by ft2 per gallon and multiplies gallons by oz per gallon; metric divides m2 by m2 per L and multiplies liters by mL per L. Tablespoon output doubles fluid ounces. Label directions override every number here including protective gear, reentry, and weather windows.
Worked example
Example: 5000 ft2 lawn
A 5000 ft2 lawn sprays 1000 ft2 per gallon with 2 oz product per gallon. Find spray, product, and spoons.
- Spray = 5000 / 1000 = 5 gal.
- Product = 5 x 2 = 10 fl oz.
- Spoons = 10 x 2 = 20 tbsp.
- Metric mirror: 464.5 m2 gives 19 L and 295.8 mL.
- Halving ground to 2500 ft2 halves all three.
- The label rate always beats this math.
Reference table
| Lawn | Spray | Product |
|---|---|---|
| 2500 ft2 | 2.5 gal | 5 fl oz |
| 5000 ft2 | 5 gal | 10 fl oz |
| 7500 ft2 | 7.5 gal | 15 fl oz |
| 10000 ft2 | 10 gal | 20 fl oz |
Limits
- Arithmetic only; label is law.
- No drift, gear, or weather modeling.
- No product or weed advice.
- Clean measuring assumed.
Common mistakes
- Eyeballing ounces in the jug cap.
- Raising rates for stubborn weeds.
- Spraying wind toward beds.
- Mixing units across systems.
- Skipping tank cleanup after.
Try it yourself
Quick checks. Answers sit tucked under each question.
Half lawn: 2500 ft2 at the same rate?
2.5 gal spray. 5 fl oz product. 10 tbsp.
Big lawn: 10000 ft2 at the same rate?
10 gal spray. 20 fl oz product. 40 tbsp.
3000 ft2 at the same rate? Work it by hand.
Spray = 3000/1000 = 3 gal. Product = 3 x 2 = 6 fl oz = 12 tbsp.
Questions
How is the mix found?
Area divided by coverage for spray volume, times the per gallon rate for product. The example gives 5 gal with 10 fl oz.
Ounces to tablespoons?
Two tablespoons per fluid ounce here. The example converts 10 fl oz to 20 tbsp for small measuring.
Does it work in liters?
Yes. Pick metric: 464.5 m2 at 24.5 m2 per L with 15.6 mL per L gives 19 L and 295.8 mL.
Can I raise the rate for weeds?
Never. Labels are law: rates, protective gear, weather limits, and sensitive areas all come from the product label first.
How do I clean gear after?
Rinse the tank, flush the boom, and run clean water through nozzles so residue never meets the next mix.
Does drift matter?
No. Overspray drifts onto beds, water, and neighbors; shields, low pressure, and calm air keep it home.