Conversions – GPD to MDG

One of the functions of our division is to offer free compliance assistance to the DEP-regulated community. The compliance assistance staff recently helped a facility regarding the methods for properly calculating gallons per day (gpd) to million gallons per day (MGD) and also calculating the average flow over the reporting period. If facilities improperly convert some of their data into their DMR, they could possibly report that they are major polluters in the DMR Pollutant Loading Tool, when in fact, these facilities are imputing overinflated numbers that could potentially put their facility out of compliance. Given the importance of properly reporting data, we thought this would be a good time to review the proper techniques in converting gallons per day into million gallons per day to ensure that our readers know the correct conversion procedures.

Here is the formula:

Gallons per Minute x 1,440 Minutes per Day = gallons per day

Next, take your gallons per day and divide it by 1,000,000.  This will give you your Million Gallons per Day Conversion.

So let’s see if we can wrap our heads around this and work through a problem.

We have 1,500 gallons per day divided by 1,000,000 = 0.001500 MGD

If we have a 31-day month with 38,000 gallons flowing during that period, what would be the average daily flow in million gallons per day (MGD)?

38,300 gallons divided by 31 days = 1,235.48 gallons per day

1,235.48 gallons per day divided by 1,000,000 = 0.00123548 MGD

There is also an online calculator that can be used where you can simply input your numbers in the appropriate box and it will give you the correct answer. However, I recommend that you only use this online calculator to doublecheck your own conversion and not depend on this tool to be available at all times.

The certification and compliance assistance staff members in our division want to see all Kentucky facilities stay in compliance. We always strive to provide operators with the proper training in order for them to operate their facility properly, efficiently and effectively. If you have any questions about conversions or the DMR Pollutant Loading Tool, you may contact us at

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