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DetailRig
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Free car detailing tool

Pressure Washer Nozzle Size Calculator

Estimate a spray tip nozzle number from your washer’s working flow and your selected target pressure. The result is a starting point for checking a manufacturer chart and a pressure gauge.

What nozzle size do I need for a pressure washer?

Pressure washer nozzle numbers use the water flow a tip would pass at a 4,000 PSI reference. Estimate the number by multiplying working flow in US GPM by the square root of 4,000 divided by desired PSI. Select an available size at or above the calculated number, then verify actual pressure with a gauge.

Pressure washer nozzle sizing

Use actual working flow if available. The example input values are not a DetailRig measurement or a universal paint safety target.

Calculated nozzle number

3.00

Next half-size up

3.0

PSI × US GPM (CU)

2700

The nozzle number is an estimate based on GPM at a nominal 4,000 PSI reference. Round up to avoid selecting a smaller orifice that could raise pressure above your target. Verify actual pressure with a gauge and consult washer and nozzle ratings. A formula cannot certify a setup as safe for paint. Need UK units? Use the PSI to bar converter.

Nozzle formula and example

Nozzle number = US GPM × √(4,000 ÷ target PSI). For an example 1.5 US GPM flow and 1,000 PSI target, the result is 3.0. The nearest available size depends on the manufacturer’s nozzle range; the displayed half-size is a convenient upper bound, not a guarantee that the item is stocked.

What the result cannot tell you

A machine’s advertised maximum pressure and flow may not occur at the same time. Pump behaviour, hose losses, nozzle wear, and fittings change working output. No PSI number alone guarantees that a spray is safe for paint: damaged paint, spray angle, distance, and dwell all matter. Follow the equipment and vehicle manuals and test a low-risk area. For UK specifications, use the PSI/bar and flow converter.

Source and calculation status

The nozzle-number convention and flow table are documented in General Pump’s nozzle chart. This calculator estimates a tip number; it is not a measured washer test or paint safety certification. Reviewed 28 September 2026.

Detailing answers

Frequently asked questions about car detailing

Clear answers to common car detailing, washing, interior-care, and paint-protection questions.

What is car detailing?

Car detailing is the careful cleaning, decontamination, and protection of a vehicle’s interior and exterior. The process can include a wash, wheel and tire care, interior cleaning, paint decontamination, polishing, and a protectant; the right steps depend on the vehicle and finish.

What products do I need for car detailing at home?

Start with car wash soap, wash media, microfiber towels, wheel cleaner, an interior cleaner, and a vacuum. Add a pressure washer, foam cannon, polisher, or paint protection only when the task and your skill level justify them.

What car wash soap should I use?

Choose a soap made for automotive paint with clear dilution instructions. A pH-neutral car soap is a common starting point for routine maintenance, but the best choice depends on the coating, soil, wash method, and manufacturer guidance. Avoid household dish detergent on vehicle finishes.

How much PSI is needed to wash a car?

There is no single PSI target for every vehicle or washer. Use the lowest pressure and widest practical spray pattern that removes soil safely, keep the nozzle moving, and follow the washer and vehicle-maker guidance. Pressure, nozzle, distance, and technique all affect risk.

What is a foam cannon used for?

A foam cannon meters car wash solution into a pressure-washer stream to apply cleaning foam. It can help pre-soak and loosen loose soil before contact washing, but foam alone does not replace a careful rinse and wash.

How do I clean a car interior?

Remove loose items and vacuum first, then clean one material at a time with a compatible product and a lightly damp microfiber or brush. Test an inconspicuous area, avoid over-wetting electronics and upholstery, and follow the material and product instructions.

What is paint correction?

Paint correction is the controlled polishing of a vehicle’s clear coat to reduce the appearance of defects such as swirls or light scratches. It removes some material, so inspect the finish, use the least aggressive effective method, and treat deep defects as a professional-risk decision.

How do I choose a dual-action polisher?

Compare the machine’s throw, speed control, ergonomics, backing-plate compatibility, power, and support—not just the wattage. Beginners generally benefit from predictable control and manageable balance; pad and compound choice also change the result.

How long does ceramic coating last?

Ceramic-coating durability depends on the formulation, preparation, layers, exposure, maintenance, and manufacturer instructions. Treat a stated lifespan as a manufacturer claim unless DetailRig has documented evidence, and plan regular washing and inspection rather than assuming permanent protection.

What should I look for in car detailing products?

Match the product to the surface, soil, tool, and task; check dilution, compatibility, safety directions, and aftercare. DetailRig labels evidence as TESTED, USED, RESEARCHED, or MANUFACTURER-CLAIM so readers can distinguish hands-on evaluation from source-based or maker-provided information.