Pressure Washer Detergent Ratio Calculator
Mix pressure-washer detergent to a dilution ratio like 1:10 for your tank, accounting for the downstream injector draw.
How it works
Detergent = total ÷ (ratio + 1) · Water = total − detergent
A 1:10 dilution splits the mix into 11 parts — one detergent, ten water — so you divide the finished volume by (ratio + 1) for the detergent share. If your machine uses a downstream (low-pressure) injector, note that it draws its own ratio from a bottle of already-mixed solution, so you may pre-dilute less aggressively; a dedicated onboard tank uses the mix as-is. Rinse the surface first, apply low-pressure detergent from the bottom up, let it dwell without drying, then rinse top down.
Worked example
A 1:10 mix in 1 gallon (128 fl oz): 128 ÷ (10 + 1) = 11.6 fl oz of detergent (about 1.5 cups) with the rest — roughly 0.91 gallon — as water.
Frequently asked questions
What ratio should I use?
Follow the detergent label; common ranges are 1:10 for tougher jobs to 1:20 for general cleaning. Start weaker and increase strength only if needed — over-concentrating wastes product and can streak or damage some surfaces.
How does a downstream injector change the math?
A downstream injector siphons detergent and dilutes it further as it mixes with the water stream, often around 1:10 on its own. If your machine injects, you can start from a less-diluted solution; an onboard detergent tank sprays the mix exactly as you made it.
Why let the detergent dwell before rinsing?
Giving the solution a few minutes to break down grime does the cleaning so the water pressure does not have to. Just do not let it dry on the surface, especially in sun, or it can leave streaks.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.