Home › Calculators › Tankless GPM Calculator
Tankless GPM Calculator
Quick answer: Peak GPM = the sum of the flow rates of every hot-water fixture you might run at the same time. Typical examples: shower 2.0, bathroom sink 1.0, kitchen sink 1.5, dishwasher 1.0, washer 2.0 GPM.
Estimates for planning only — not professional, engineering, plumbing, gas or electrical advice. Confirm sizing, venting, gas and electrical with a licensed installer and local code.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
2 showers (2 × 2.0) + kitchen sink (1.5) = 5.5 GPM peak. Check your actual fixtures — low-flow showerheads may be 1.5–1.8 GPM.
Back to Tankless size calculator · Home