Spray Tank Calculator
Find the total spray water and number of tank fills for your field, and the area one tank covers.
Enter your details
Before you start spraying, know how much water to arrange and how many times you'll refill. Enter your area, the water you spray per acre and your tank size to get the number of tank fills and the area covered by each tank.
About the Spray Tank Calculator
Spraying takes planning. You need enough clean water on hand, enough product for all the tank fills, and a way to make sure each tank covers the right patch of ground. If one tank is supposed to cover 1/10th of an acre but you walk faster than usual, the last strip of the field gets nothing.
This calculator tells you three things:
- Total water – so you can arrange a drum, tanker or pipe connection.
- Tank fills – so you know how much product to prepare and roughly how long the job will take.
- Area per tank – so you can mark out the field (for example with sticks every few rows) and check you're on track.
Once you know the number of tanks, use the Pesticide Dilution Calculator to work out how much product goes into each one.
How to use the Spray Tank Calculator
- 1 Enter the area you are spraying.
- 2 Enter how much water you spray per acre (or per hectare).
- 3 Enter your tank capacity – 16 L for most knapsack sprayers.
- 4 Press Calculate.
The formula we use
Total water = Spray volume per acre × Acres
Tank fills = Total water ÷ Tank capacity
Area per tank = Tank capacity ÷ Spray volume per acreWorked example
You need to spray 3 acres at 150 L per acre with a 16 L knapsack sprayer.
- Total water = 150 × 3 = 450 L.
- Tank fills = 450 ÷ 16 = 28.1, so plan for 29 fills.
- One tank covers 16 ÷ 150 = 0.107 acre, or about 432 m² – roughly a 20 m × 21.6 m block.
Things to keep in mind
- Know your real spray volume. Calibrate by spraying a measured area with a full tank at normal speed. Nozzle type, pressure and walking speed all change it.
- Crop stage changes water needs. Young crops need less water per acre for good coverage than tall, dense crops.
- Use clean water. Muddy or very hard water can clog nozzles and reduce the effect of some products.
Frequently asked questions
How much water is needed to spray one acre?
For knapsack spraying of field crops, 150–200 L per acre is common. Some products and crops specify different volumes, so check the label. Drones use far less water.
How many 16-litre tanks are needed for one acre?
At 200 L per acre, 12.5 tanks; at 150 L per acre, about 9.4 tanks.
How do I calibrate a knapsack sprayer?
Mark out a known area (say 100 m²), fill the tank with a measured amount of water, spray the area at your normal pace and pressure, then measure what's left. Water used ÷ area × 4,047 gives your litres per acre.
Guides that use this calculator
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