After you buying a drone, you will consider how to increase your flight times.  

I found a formula for quadcopter flight time calculator

Quadcopter flight times =(Battery Capacity * Battery Discharge /Average Amp Draw)*60



How about this calculator formula? For instance, If have a lipo battery 3s 3300mAh, I calculated the average  amp draw of quadcopter to be around 20 amps, and I am making an  assumption that 80% of battery capacity will is used, then the  quadcopter flight time is 7,92 minutes.

Based on this theoretical value, my flight time maybe around or less than 7,92 minutes.

What do you think?

Not a great deal of practical use really, as the power consumption of the aircraft will vary according to what it is doing, the current draw is not constant. When climbing or hovering, it uses more power than descending or flying forward. And your calculation does not take into account the state of charge of the battery at the beginning of the flight. For something that is dynamic live power consumption, you can't use average figures.

You'll find quite accurate flight times (in perfect conditions) for all Phantoms in the manual and spec sheets.

If you're racing or the like with mini quads then you won't get 7 minutes from a 3s 3300mah battery. I can get 3.5 minutes from a 3s 1500mah , maybe 4 mins from a 3s 2200mah at gentle speeds. You won't get much more from 3300 because of the extra weight - diminishing returns

Matt-and-Riley Posted at 2017-4-17 00:59
You'll find quite accurate flight times (in perfect conditions) for all Phantoms in the manual and spec sheets.

If you're racing or the like with mini quads then you won't get 7 minutes from a 3s 3300mah battery. I can get 3.5 minutes from a 3s 1500mah , maybe 4 mins from a 3s 2200mah at gentle speeds. You won't get much more from 3300 because of the extra weight - diminishing returns

YES, Bigger lipo battery can be powered more energy. In fact As the battery gets larger, the increase in flight time becomes ineffective, because of the weight of battery.

But we have to consider all the weight of parts when calcute Average Amp Draw, For example (From above article)
If  each motor draws 1 amps to produce 100g of thrust. if your quadcopter take 2000g(including all parts) to flight, each motor will have to produce 500g (500g = 2000g / 4 motors) of thrust in order to hover. Then your quadcopter Average Amp Draw is 20AMPS ( 20AMPS =4motors * 500g/100g per 1amps);