Enter your sprayer details
Choose a mode: estimate from your current tank, or plan a job by target area and application rate.
Example data table
Sample values show how changing nozzles and pauses affects elapsed time and refills.
| Tank | Nozzles | Flow/nozzle | Efficiency | Pauses | Spray time | Elapsed time | Target area | Refills |
|---|---|---|---|---|---|---|---|---|
| 15 L @ 85% | 1 | 1.2 L/min | 95% | 10% | 9.6 min | 10.7 min | 250 m² | 1 |
| 15 L @ 85% | 2 | 1.2 L/min | 95% | 10% | 4.8 min | 5.3 min | 250 m² | 2 |
| 4 gal @ 75% | 1 | 0.35 gal/min | 90% | 20% | 7.7 min | 9.6 min | 3,000 ft² | 1 |
Formula used
How to use this calculator
- Pick a mode: use From tank to estimate runtime, or From target area to plan a full job.
- Enter tank details: set tank capacity, fill amount, and a small reserve to avoid running dry.
- Add nozzle and flow: select nozzle count and the flow per nozzle from your nozzle chart.
- Adjust realism: set an efficiency factor and pause percent to reflect real working conditions.
- For area planning: enter target area and application rate to estimate liquid needed and refills.
- Download results: after calculation, use the CSV or PDF buttons to save your numbers.
Field notes and planning data
Calibration benchmarks for consistent output
Most backpack sprayers deliver repeatable flow only after a short prime. Record a one minute catch test per nozzle at your usual pressure, then save that number as flow per nozzle. A 1.2 L/min tip will empty 10 L in about 8.3 minutes of trigger time, before efficiency and reserve adjustments each time.
Nozzle flow, pressure, and pattern choices
Flow typically increases with pressure, while droplet size decreases. Fine droplets improve leaf coverage yet drift more in wind. For bed edges and ornamentals, lower pressure with a fan tip often reduces bounce and overspray. When you switch tips, update flow and recheck runtime, because doubling nozzles doubles total flow.
Tank utilization, reserve volume, and mixing safety
Leaving a small reserve helps avoid sucking air and losing calibration. If you keep 0.5 L reserved and fill 85% of a 15 L tank, your working liquid starts near 12.25 L, then drops by the reserve and efficiency factor. Use the estimator to plan mixes so you do not over dilute or waste product.
Pause allowances and refill pacing
Real jobs include walking, aiming, and pump strokes. A 10% pause factor turns 10 minutes of spraying into about 11.1 minutes elapsed. For larger areas, refills dominate. If each refill takes 4 minutes and you need three refills, that adds 12 minutes on top of spraying and pauses, guiding realistic work blocks.
Coverage planning by area and application rate
Label directions often specify volume per area, such as liters per 100 square meters or gallons per 1,000 square feet. Multiply your target area by the chosen rate to estimate total liquid needed, then compare to per tank available volume. This supports scheduling, staffing, and compliant application records for lawns and garden beds. Track temperature and viscosity too; colder mixes can spray slower and change pattern quality. Keep notes per product, because surfactants can shift flow slightly. Updating values makes runtime estimates dependable across seasons.
FAQs
Why does elapsed time differ from spray time?
Spray time assumes the trigger is on continuously. Elapsed time adds pauses for walking, turning, pumping, and repositioning, using the pause percentage to scale trigger time into realistic wall clock time.
What efficiency value should I use?
Start with 90–95% for careful spot treatments. Use 80–90% for windy sites, dense foliage, or frequent priming. Improve efficiency by calibrating, keeping a steady pace, and maintaining correct pressure.
How do I find flow per nozzle?
Run clean water at normal pressure for one minute into a marked container. Measure the collected volume. That number is your liters per minute; repeat twice and average to reduce error.
Should I enter fill percent or exact volume?
Use fill percent for quick estimates when you do not measure precisely. Use exact volume when mixing a specific batch. Both methods convert to the same internal volume for calculations.
How are refills estimated in area mode?
The estimator divides total needed volume by per tank available volume after reserve and efficiency. It rounds up to whole tanks, then counts refills as tanks minus one, adding your refill time.
Can this help with different units?
Yes. You can switch between liters and gallons for tank inputs, and between square meters and square feet for area planning. The calculator converts units internally to keep the math consistent.