Reverse Osmosis System Calculator
Size your RO system. Choose residential (by people) or commercial (by daily gallons).
Sizing notes
Rated GPD is measured at ideal conditions — cold water and high TDS lower real output, so size up. Commercial systems must be pretreated (sediment, carbon, and a softener ahead of the membranes). See our Commercial RO Sizing Guide.
Frequently asked questions
What size reverse osmosis system do I need?
For a home, a 50–100 GPD under-sink RO covers drinking and cooking. For commercial use, total your daily gallons, add ~40% margin, and adjust for feed temperature and TDS.
Does RO output equal the rated GPD?
No — rated GPD is at ideal warm, low-TDS conditions. Cold or high-TDS feed water reduces real output, so size up and use a pressure tank for demand.
Do I need pretreatment for RO?
Yes. Sediment and carbon prefilters protect the membrane, and a softener ahead of a commercial RO prevents hardness scaling — the #1 cause of short membrane life.