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DIY Cost Tools

DIY Cost Tools

Sump Pump Capacity Calculator

Apply a safety factor to measured sump inflow and report the pump capacity needed at the entered total dynamic head.

gal/min
Enter a number from 0.01 to 100000.
multiplier
Enter a number from 1 to 5.
ft
Enter a number from 0 to 300.

Use the units shown. Blanks, words, comma-formatted numbers, fractions, non-finite values and values outside the stated ranges are rejected.

Required pump capacity
Required hourly capacity
Required rating point

How to use this calculator

  1. Replace every example value with your own measurements, label values or planning assumptions.
  2. Keep each value in the unit printed beside its field.
  3. Select Calculate, then compare the result with the formula and limitations below.

Formula and method

Required gallons per minute = measured inflow × safety factor. Hourly capacity = required gallons per minute × 60. The pump curve must provide this flow at the entered head.

Results are hidden whenever an input changes or validation fails, so an older answer cannot be mistaken for the current calculation.

Worked example

Measured inflow = 15 gal/min; Safety factor = 1.5 multiplier; Total dynamic head = 10 ft. The calculator returns Required pump capacity = 22.5 gal/min; Required hourly capacity = 1350 gal/hr; Required rating point = 22.5 gal/min at 10.0 ft head.

The worked example uses the same default values displayed in the calculator.

Limitations and safety

Do not select a pump by horsepower alone. Measure inflow safely, include pipe friction and vertical lift in total dynamic head, check the manufacturer pump curve, and follow electrical and plumbing codes.

Frequently asked questions

What should I enter first?

Start with measurements or rates from the project, product label, service quote or equipment specification. Replace every example value before relying on the estimate.

Why can the real result differ?

Do not select a pump by horsepower alone. Measure inflow safely, include pipe friction and vertical lift in total dynamic head, check the manufacturer pump curve, and follow electrical and plumbing codes.

Does the calculator round purchases up?

Only outputs labeled as whole packages, vents, heaters, pails or similar counts are rounded up. Keep extra precision for planning and follow supplier packaging.

Review notes and reference

Reviewed October 5, 2026. The formula was independently checked against the displayed default example, and the calculator was tested for valid defaults, empty input, invalid formats, range boundaries and recovery. Reference: NIST SI Units. Explanations and examples are original.

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