Flow and system inputs
Enter a source flow, choose units, and expand the advanced sections for operational analysis.
Formula used
MGD means million gallons per day. GPM means gallons per minute. A day contains 1,440 minutes, so the standard conversion assumes the daily volume is spread evenly across every minute of the day.
Therefore, one MGD equals approximately 694.444444 GPM. The exact result depends only on the unit definitions. It does not depend on pipe size, pump efficiency, or water temperature.
Limited operating schedule formula
Some pumps run fewer than 24 hours daily. The same daily volume must then pass during fewer minutes. This increases the required operating flow.
Flow per operating pump
Pipe velocity
How to use this calculator
- Enter the flow value and choose its source unit.
- Select the unit you want to calculate.
- Choose continuous operation or enter a limited daily schedule.
- Add a peaking factor when evaluating high-demand conditions.
- Enter operating and standby pump counts for capacity distribution.
- Use a tank volume to estimate fill or drain time.
- Enter an inside pipe diameter to calculate average velocity.
- Select decimal precision and calculate the result.
The primary answer appears above the form. Detailed flow, pump, storage, and pipe results appear below it. Use the copy, print, and history controls to keep useful calculations.
Understanding MGD and GPM
MGD is widely used for municipal water supply, wastewater treatment, industrial process water, stormwater planning, and utility reporting. It expresses a very large daily volume in a compact form. A facility processing 2 MGD handles two million US gallons during a typical day.
GPM describes a rate that is easier to connect with pumps, valves, meters, pipes, and equipment. Pump curves are commonly labeled in GPM. Converting MGD into GPM helps translate a planning flow into a mechanical operating requirement.
The standard result is an average rate. Actual systems rarely operate at one perfectly constant rate. Demand may rise during mornings, fall overnight, or change with rainfall. Engineers therefore evaluate average flow, peak flow, minimum flow, and emergency conditions separately.
Why operating hours matter
A one MGD process running continuously needs about 694.44 GPM. If it runs only twelve hours daily, it needs about 1,388.89 GPM while operating. The daily volume is unchanged. The instantaneous equipment duty doubles because the available operating time is cut in half.
Average and peak conditions
Peaking factors convert an average rate into a planning peak. A factor of 2.5 multiplies the selected flow by 2.5. Project-specific criteria should come from actual records, regulatory guidance, design standards, and the intended level of service.
Pump capacity and standby planning
Pump selection requires more than a unit conversion. The duty point also depends on total dynamic head, static lift, friction loss, minor losses, pump curve shape, motor rating, fluid properties, and control strategy. This calculator focuses on flow allocation and capacity checks.
Operating pumps share the selected design flow. Standby pumps add reliability. An N+1 arrangement generally means enough installed units remain to meet the required duty after one unit is unavailable. Whether full capacity must remain available during an outage depends on the facility and governing criteria.
Reserve and planning margins
A reserve percentage adds direct spare flow capacity. A planning margin can represent forecast growth, uncertainty, or an owner-selected allowance. Avoid stacking several factors without understanding them. Peak factors, reserve capacity, growth allowances, and equipment derating can overlap.
Efficiency input
Efficiency alone does not determine rated flow. It primarily affects power requirements. The efficiency-adjusted flow shown here is a reference ratio, not a substitute for hydraulic power calculations. A full pump power analysis needs head and fluid density.
Storage and pipeline checks
Tank filling time is calculated by dividing usable tank volume by net inflow. Real tanks may fill while water is being withdrawn. In that case, use the net difference between inflow and outflow rather than the gross pump rate.
Pipe velocity is based on the entered inside diameter. Nominal pipe size is not always the actual internal diameter. Material, pressure class, wall thickness, lining, scale, and age can change the open area.
The calculator also estimates a diameter for a selected target velocity. This is an early screening result. Final pipe sizing should evaluate head loss, surge, water hammer, minimum cleansing velocity, pressure limits, material requirements, and lifecycle costs.
Worked examples
Example 1: one MGD to GPM
Multiply one by one million gallons. Divide the result by 1,440 minutes. The answer is 694.444444 GPM.
Example 2: five MGD to GPM
Five MGD equals five million gallons daily. Dividing by 1,440 gives 3,472.222222 GPM.
Example 3: two MGD during sixteen hours
Sixteen hours contains 960 minutes. Divide two million gallons by 960 minutes. The operating requirement is 2,083.333333 GPM.
Example 4: pump distribution
Suppose a peak operating requirement is 3,000 GPM and three pumps operate together. Each operating pump must provide 1,000 GPM before adding reserve or margin.
Frequently asked questions
How many GPM are in one MGD?
One MGD equals approximately 694.444444 GPM when flow is continuous for 24 hours.
Does one MGD always equal 694.44 GPM?
It does as an average daily conversion. A pump operating fewer than 1,440 minutes needs a higher operating GPM to move the same volume.
Can this calculator convert GPM back to MGD?
Yes. Select GPM as the source unit and MGD as the destination unit.
What peaking factor should I use?
Use project records or applicable design criteria. There is no universal factor for every water or wastewater system.
Can I size a pump from GPM alone?
No. Pump selection also requires head, system curve, efficiency, motor power, fluid properties, and operating controls.
Why is pipe velocity zero?
Pipe velocity is calculated only when a positive inside diameter is entered.
What tank volume should I enter?
Use the usable operating volume, not necessarily the total geometric capacity.
Does the calculator account for simultaneous tank outflow?
No. Enter or calculate net flow when inflow and outflow occur together.
What is N-1 capacity?
It is the capacity remaining after one installed pump is unavailable.
Are the results suitable for final design?
They are useful for conversion and preliminary checks. Final design requires project-specific engineering review.
MGD to GPM reference table
These values assume continuous flow over 1,440 minutes per day.
| MGD | GPM | GPH | GPD |
|---|---|---|---|
| 0.001 MGD | 0.694444 GPM | 41.667 GPH | 1,000 GPD |
| 0.005 MGD | 3.472222 GPM | 208.333 GPH | 5,000 GPD |
| 0.01 MGD | 6.944444 GPM | 416.667 GPH | 10,000 GPD |
| 0.025 MGD | 17.361111 GPM | 1,041.667 GPH | 25,000 GPD |
| 0.05 MGD | 34.722222 GPM | 2,083.333 GPH | 50,000 GPD |
| 0.1 MGD | 69.444444 GPM | 4,166.667 GPH | 100,000 GPD |
| 0.25 MGD | 173.611111 GPM | 10,416.667 GPH | 250,000 GPD |
| 0.5 MGD | 347.222222 GPM | 20,833.333 GPH | 500,000 GPD |
| 0.75 MGD | 520.833333 GPM | 31,250 GPH | 750,000 GPD |
| 1 MGD | 694.444444 GPM | 41,666.667 GPH | 1,000,000 GPD |
| 1.5 MGD | 1,041.666667 GPM | 62,500 GPH | 1,500,000 GPD |
| 2 MGD | 1,388.888889 GPM | 83,333.333 GPH | 2,000,000 GPD |
| 2.5 MGD | 1,736.111111 GPM | 104,166.667 GPH | 2,500,000 GPD |
| 3 MGD | 2,083.333333 GPM | 125,000 GPH | 3,000,000 GPD |
| 4 MGD | 2,777.777778 GPM | 166,666.667 GPH | 4,000,000 GPD |
| 5 MGD | 3,472.222222 GPM | 208,333.333 GPH | 5,000,000 GPD |
| 7.5 MGD | 5,208.333333 GPM | 312,500 GPH | 7,500,000 GPD |
| 10 MGD | 6,944.444444 GPM | 416,666.667 GPH | 10,000,000 GPD |
| 15 MGD | 10,416.666667 GPM | 625,000 GPH | 15,000,000 GPD |
| 20 MGD | 13,888.888889 GPM | 833,333.333 GPH | 20,000,000 GPD |
| 25 MGD | 17,361.111111 GPM | 1,041,666.667 GPH | 25,000,000 GPD |
| 50 MGD | 34,722.222222 GPM | 2,083,333.333 GPH | 50,000,000 GPD |
| 75 MGD | 52,083.333333 GPM | 3,125,000 GPH | 75,000,000 GPD |
| 100 MGD | 69,444.444444 GPM | 4,166,666.667 GPH | 100,000,000 GPD |
| 250 MGD | 173,611.111111 GPM | 10,416,666.667 GPH | 250,000,000 GPD |
| 500 MGD | 347,222.222222 GPM | 20,833,333.333 GPH | 500,000,000 GPD |