Calculator Inputs
Example Data Table
| Surface | Area (sq ft) | GPM | PSI | Nozzle | Soil | Total time (hh:mm) | Water (gal) |
|---|---|---|---|---|---|---|---|
| Concrete patio / walkway | 300 | 2.5 | 3000 | 25° (general) | Medium dirt | 02:08 | 5.3 |
| Wood deck / steps | 220 | 2.0 | 2500 | 40° (wide) | Light dust | 02:04 | 4.1 |
| Pavers / brick path | 450 | 3.0 | 3200 | 15° (narrow) | Algae / mold staining | 03:38 | 10.9 |
Formula Used
The calculator estimates an effective cleaning rate in square feet per minute, then divides area by that rate.
How to Use This Calculator
- Measure the surface area and choose units.
- Select the surface type and soil level.
- Enter your washer’s flow rate (GPM) and pressure (PSI).
- Pick a nozzle angle and technique to match your risk level.
- Set overlap and efficiency to reflect obstacles and edging.
- Add setup and break time for a realistic schedule.
- Click Calculate to see time, water, and detergent estimates.
Surface condition drives production rate
Time on site is dominated by how quickly soil releases from the surface. Light dust often clears in one or two passes, while algae or embedded grime can require slower, overlapping passes plus a dwell period for detergent. In the calculator, soil level and overlap reduce the effective rate so the schedule remains realistic.
Flow and pressure contribute differently
Flow rate typically improves coverage and rinsing speed because more water carries loosened debris away. Pressure helps break bonds on hard stains, but gains can be smaller once a practical threshold is reached. The model scales rate with flow more strongly than pressure to match common field behavior in garden cleaning tasks.
Technique and protection steps add measurable minutes
Protecting nearby plants, moving furniture, covering outlets, and setting safe spray distance all reduce pace. A “Careful” technique setting intentionally slows production to reduce risk on wood, grout, and delicate finishes. Setup and break minutes capture hose routing, refills, and short rests that occur on larger jobs.
Water planning supports safer, consistent work
Water use is estimated from flow rate multiplied by total runtime. This helps plan hose capacity, tank refills, and runoff control. If you dose detergent, the calculator multiplies gallons by your selected ounces-per-gallon to estimate product needs and avoid under-mixing or waste.
Example data for quick calibration
Use one measured test patch to refine inputs. For example, a 50 sq ft concrete patch at 2.5 GPM, 3000 PSI, 25° nozzle, medium dirt, 10% overlap, and 85% efficiency often takes about 18–22 minutes including edging. If your patch time is higher, increase overlap, lower efficiency, or choose heavier soil to match reality.
| Test patch | Area (sq ft) | Inputs | Observed time (min) | Suggested adjustment |
|---|---|---|---|---|
| Concrete corner | 50 | 2.5 GPM, 3000 PSI, 25°, medium dirt | 22 | Set efficiency to 80% and overlap to 15% |
| Deck step section | 40 | 2.0 GPM, 2500 PSI, 40°, light dust | 20 | Choose “Careful” technique for safer pacing |
| Paver strip | 60 | 3.0 GPM, 3200 PSI, 15°, algae staining | 35 | Select algae soil level and keep 20% overlap |
FAQs
1) Why does my job take longer than the estimate?
Edges, corners, obstacles, and stubborn staining reduce pace. Lower the efficiency value, increase overlap, or choose a heavier soil level to reflect real conditions. A small timed test patch improves accuracy quickly.
2) What nozzle should I use around plants?
A wider nozzle like 40° reduces impact and helps protect leaves and mulch. Work from farther away and avoid spraying directly into beds. Use the “Careful” technique setting to reflect slower, safer passes.
3) Does higher PSI always clean faster?
Not always. Pressure can help break tough bonds, but flow rate often improves coverage and rinsing speed. If pressure is already adequate, better technique and overlap choices can matter more than adding PSI.
4) How do I pick an efficiency percentage?
Use 90–95% for open, unobstructed slabs, 80–90% for typical patios with edging, and 70–80% for tight spaces, furniture, steps, and frequent repositioning. If unsure, start at 85% and adjust after a test patch.
5) Should I include detergent dwell time?
Yes, if you apply detergent and wait for it to work. Add the dwell period into “Break / refill minutes” so total time reflects real workflow. Always follow the product label and rinse thoroughly near plants.
6) Why include overlap between passes?
Overlap prevents striping and ensures consistent cleaning, especially on textured surfaces. However, overlap increases time because you are re-covering area. If striping is visible, increase overlap before raising pressure.
7) Can I use square meters instead of square feet?
Yes. Select m² in the area unit dropdown. The calculator converts to square feet internally for consistent rates, then returns time, water, and detergent estimates based on your chosen settings.