Recommended PSI
3000 PSI
GPM
2.5
Time
2.0 hrs
Water
300 gal
Required Specs
3000 PSI
2.5 GPM \u2022 7,500 CU
Time
2.0 hrs
Water
300 gal
✓ Gas (Light) is adequate
Inputs
Result
Concrete requires 3,000 PSI with 2.5 GPM. At 250 sq ft/hr, 500 sq ft takes ~2 hours. Water usage: 2.5 GPM × 120 min = 300 gallons.
Inputs
Result
Cars need only 1,500 PSI to avoid paint damage. At 150 sq ft/hr, ~40 minutes. Water: 1.4 GPM × 40 min = 56 gallons. Electric washer is adequate.
PSI requirements vary by surface. Cars need only 1,200–1,500 PSI, wood decks need 1,500–2,000 PSI, and concrete driveways need 3,000–3,500 PSI. Using too much pressure damages surfaces; too little won't clean effectively.
| Surface | PSI Range | GPM | Nozzle Tip |
|---|---|---|---|
| Car / Boat | 1,200–1,500 | 1.4+ | 40° white |
| Wood Deck | 1,500–2,000 | 1.4+ | 25° green |
| Concrete | 3,000–3,500 | 2.5+ | 15° yellow |
| Paint Strip | 3,500–4,000 | 3.0+ | 15° yellow |
PSI (pounds per square inch) is the water pressure — the force that breaks dirt loose from the surface. GPM (gallons per minute) is the water flow — the volume that rinses the loosened dirt away. You need both: high PSI without enough GPM leaves streaks; high GPM without PSI won't clean.
Electric pressure washers (1,300–2,200 PSI) are lighter, quieter, and adequate for cars, patios, and light siding work. Gas washers (2,500–4,400 PSI) are needed for concrete, heavy stains, paint stripping, and commercial work. Gas units cost more and require engine maintenance.
Nozzle tips are color-coded by spray angle. Wider angles (40°–65°) spread the force over more area for gentle cleaning. Narrower angles (0°–15°) concentrate force for tough stains. Start with a wide nozzle and step down only if needed.
Read our guide
Read our guide
Calculate electricity cost for electric washers
Fuel cost for running a generator with your washer
Calculate paint needed for your home exterior
Plan your deck project
Explore all our free tools and utility calculators
Last Updated: Mar 19, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.