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To convert gallons per minute (gpm) to million gallons per day (MGD), multiply gallons per minute by 1,440 minutes per day and divide by 1,000,000 gallons per million gallons; equivalently, divide gpm by 694.4. Every conversion on an operator exam works the same way: write the quantity with its units, multiply by conversion factors arranged so the unwanted units cancel top and bottom, and read the answer's units off what is left.
MGD = gpm × 1,440 min/day ÷ 1,000,000 gal/million gallons (MG)
| Term | Meaning | Units |
|---|---|---|
| gpm | flow rate | gal/min |
| 1,440 | minutes in one day | min/day |
| 1,000,000 | gallons in one million gallons | gal/MG |
| MGD | flow rate | MG/day |
The minutes-per-day factor and the MGD-to-gpm equivalence both appear on these sheets, alongside 7.48 gal/ft³ and the psi-to-feet factors. Official sheets: Exam Conversion Sheet (revised 4/30/2026) (State Water Resources Control Board, Drinking Water Operator Certification Program; Water Treatment and Water Distribution exams); Equivalents and Formulas Sheet, Version 1 (State Water Resources Control Board, Wastewater Operator Certification Program; Wastewater Treatment Plant Operator exams); Equivalents and Formulas Sheet, Version 2 (State Water Resources Control Board, Wastewater Operator Certification Program; Wastewater Treatment Plant Operator exams).
Unit conversions · Original practice item, not a real exam question.
A high-service pump station runs at 2,300 gpm around the clock. Express that flow in MGD.
2,300 gal/min × 1,440 min/day3,312,000 gal/day × 1 MG / 1,000,000 gal= 3.312 MG/dayAnswer: 3.312 MGD
One million gallons spread over the 1,440 minutes in a day is 1,000,000 ÷ 1,440 = 694.4 gallons per minute. Dividing gpm by 694.4 is the whole conversion in one step.
One psi supports 2.31 feet of water, and one foot of water exerts 0.433 psi; the two factors are reciprocals. A gauge reading 50 psi therefore represents 50 × 2.31 = 115.5 feet of head, and 115.5 × 0.433 = 50.0 psi brings it back.
The certifying body's sheet prints the common factors, so the skill tested is orienting them correctly. If the unit you want to remove is on top, put it on the bottom of the next factor.
The free study app has a step-by-step lesson on this calculation, with fraction-tile unit cancellation and graded practice problems.
Open the unit conversions lessonFormulas follow the official sheets linked above, which are the reference at the exam. The worked example and the mistakes are original practice material written for this page; they are not real exam questions, which are confidential. Written by the site's author.
Questions, flashcards, and explanations are AI-written under a sourcing policy that builds on the exam content outlines and candidate materials each certifying body publishes without restriction and the regulations and technical references they cite, and that excludes actual exam questions, recollections of any exam sat by the author, other study products, and any handbook or document released under a confidentiality agreement. Any item found outside that policy is rewritten from primary sources or removed. Content is then put through repeated review — regulatory values checked against primary sources, every calculation recomputed, and errors corrected — plus spot checks by the author, who holds California water operator certifications and a California civil engineering license. Those spot checks are sampling, not a professional review: nothing here is stamped, sealed, or offered as engineering advice, and not every item has been individually verified, so mistakes can still slip through.
Not affiliated with or endorsed by the State Water Resources Control Board (SWRCB), its Division of Drinking Water (DDW) or Wastewater Operator Certification Program (WWOCP), the California-Nevada American Water Works Association (CA-NV AWWA), the California Water Environment Association (CWEA), the National Council of Examiners for Engineering and Surveying (NCEES), the California Board for Professional Engineers, Land Surveyors, and Geologists (BPELSG), the Contractors State License Board (CSLB), or the American Public Works Association (APWA). All questions, flashcards, and references are independent study aids; verify against the official exam materials.