Water operator math tutorial
Flow Unit Conversions (gpm to MGD)
Convert gallons per minute to million gallons per day.
Operators move between gpm, gpd, MGD, and cfs all day. The most common conversion on exams is gpm to MGD, because pump flows are in gpm and plant flows are in MGD.
Multiply by 1,440 minutes per day to get gallons per day, then divide by one million.
The formula
MGD = flow (gpm) × 1,440 min/day ÷ 1,000,000
| Variable | Unit |
|---|---|
| Flow | gpm |
| Result: Flow | MGD |
Conversion factors used: 1,440 minutes per day; 1 MGD = 694.4 gpm; 1 MGD = 1.547 cfs; 1 cfs = 448.8 gpm.
Applies to: Water Treatment, Water Distribution, Wastewater Treatment, Collection Systems.
Common exam tip: Memorize 694 gpm as one MGD. It lets you sanity-check any conversion in seconds.
Calculator
Flow
1 MGD
- 1. 694 gpm × 1,440 = 999,360 gpd
- 2. 999,360 gpd ÷ 1,000,000 = 1 MGD
For instructional use. Results assume the standard conversion factors shown on this page. Actual field calculations may need chemical strength, density, temperature, and other adjustments, so check your plant’s procedures.
Worked examples
Example 1
A well pump delivers 694 gpm.
- 694 gpm × 1,440 = 999,360 gpd
- 999,360 gpd ÷ 1,000,000 = 1 MGD
Answer: 1 MGD
Example 2
A plant averages 3,500 gpm.
- 3,500 gpm × 1,440 = 5,040,000 gpd
- 5,040,000 gpd ÷ 1,000,000 = 5.04 MGD
Answer: 5.04 MGD
Common mistakes
Wrong result: 0.04 MGD
using 60 minutes instead of 1,440
Wrong result: 0.65 MGD
applying the cfs factor when converting gpm to MGD
Practice questions
1. 1,000 gpm is how many MGD?
- A0.06 MGD
- B0.93 MGD
- C1.44 MGD
- D14.4 MGD
Show answer and explanation
Correct answer: C. 1,000 gpm × 1,440 = 1,440,000 gpd 1,440,000 gpd ÷ 1,000,000 = 1.44 MGD Answer: 1.44 MGD. A common slip is using 60 minutes instead of 1,440, which gives 0.06 MGD.
2. 250 gpm is how many MGD?
- A0.02 MGD
- B0.23 MGD
- C3.6 MGD
- D0.36 MGD
Show answer and explanation
Correct answer: D. 250 gpm × 1,440 = 360,000 gpd 360,000 gpd ÷ 1,000,000 = 0.36 MGD Answer: 0.36 MGD. A common slip is using 60 minutes instead of 1,440, which gives 0.02 MGD.
3. 5,200 gpm is how many MGD?
- A7.49 MGD
- B0.31 MGD
- C4.84 MGD
- D74.9 MGD
Show answer and explanation
Correct answer: A. 5,200 gpm × 1,440 = 7,488,000 gpd 7,488,000 gpd ÷ 1,000,000 = 7.49 MGD Answer: 7.49 MGD. A common slip is using 60 minutes instead of 1,440, which gives 0.31 MGD.
Where this formula applies
This calculation can appear in the disciplines below. Exact exam coverage depends on your state, certification level, and official exam outline.
Water Treatment
Water Distribution
Wastewater Treatment
Collection Systems
Study guides
Keep going with the full guide
Water Operator Math Made Simple walks through operator math step by step and includes printable references plus a full practice exam.
Water Operator Math Made Simple
A Step-by-Step Guide to the Math Every Water Operator Needs to Know