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US gallons per minute to MGD
GPM measures a flow per minute. MGD measures that flow in millions of US liquid gallons per fixed 24-hour day. Both the time period and the scale change.
The conversion
MGD = US GPM × 1,440 ÷ 1,000,000 = US GPM × 0.00144
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Why the factor works
A fixed day has 24 × 60 = 1,440 minutes. Multiply the per-minute rate by 1,440 to express it per day, then divide by one million. At an average 100 US gallons/minute, the equivalent daily rate is 144,000 US gallons/day, or 0.144 MGD.
Conversion table
Values below use unrounded factors and display up to ten significant digits.
| US gal/min | million US gal/day |
|---|---|
| 1 | 0.00144 |
| 10 | 0.0144 |
| 50 | 0.072 |
| 100 | 0.144 |
| 250 | 0.36 |
| 500 | 0.72 |
| 1,000 | 1.44 |
Reverse the conversion
To convert MGD back to US GPM, divide by 0.00144. For example, 0.72 MGD ÷ 0.00144 = 500 US GPM. This reverses the conversion without substituting a rounded factor such as 694.
Common unit mistakes
Do not read 0.144 MGD as 0.144 gallons/day. The M means million here. A rate conversion does not establish how much water actually passed during a varying-flow day; that requires an average rate over the interval or a volume measurement.
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Definitions and limits
US liquid gallon = 231 cubic inches = 3.785411784 liters. One cubic foot = 1,728 cubic inches. One cubic meter = 1,000 liters. Time conversions use fixed durations. See NIST’s conversion factors and our factors and rounding guide.
These are educational arithmetic examples. A rate is constant or an average over the stated interval. This tool does not supply operational decisions, dosing instructions or exam certification.
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