One of the main considerations when building or buying a drone is flight time. Yet, although it’s such an important factor, it’s actually quite hard to calculate. Our simple flight time calculator isn’t designed to accurately predict flight time down to the second, but it should help you to quickly get a ballpark idea of what you can expect from your setup.
The calculator requires input values for: battery capacity (Ah), discharge (%) and average amp draw (A).
Battery Capacity: This value can usually be found printed on your battery. The greater the number, the more energy the battery stores. Normally the value will be given in mAh (milliamp hours). The flight time calculator requires the value to be given in Ah (amp hours). To convert from mAh to Ah, divide by 1000. For example, enter 2.2Ah for a 2200mAh battery.
Discharge: LiPo batteries can be permanently damaged if they are fully discharged. In respect of this, it's common practice to not discharge your LiPo batteries below 20% mAh during flight; this is known as the '80% rule'. To represent this in the flight time calculator enter the value 80% in the discharge field.
Average Amp Draw: To work out the value for average amp draw, you’ll need to know the all up weight (AUW) of your drone and relate this to thrust and amp values found in the datasheet for your motor/prop configuration. The idea is to work out how many amps your multirotor will draw to maintain a stable hover (note we are taking a stable hover to represent average flight). For example, if your quadcopter has an AUW of 2kg, each motor will have to produce 500g of thrust in order to hover. If each motor draws 4amps to produce 500g of thrust, then your average current draw will be 16amps.
Obviously this is a very simplistic calculator as it doesn’t take into account numerous factors, among them flying styling and weather conditions. Whenever you do any maneuvering, other than a controlled steady hover in calm air, one or more of the motors will have to spin faster, and thus pull more current. This higher current draw will reduce flight time, so you should bear this in mind when thinking about the calculated flight time. For aerial photography work, where there is minimal moving around, you should start with about 75% of the calculated flight time. Flying in a strong cross wind can also have a huge effect on the current draw of the motors. In some cases, it can cut the flying time by as much as 50%! Finally, if you are involved in FPV racing, and are flying at high throttle levels, your flight times will degrade dramatically. Depending on how hard you are flying, FPV racing can take 3 to 4 times as much current as stable hovering does.
If you would like to more accurately model your multirotor setup and evaluate lots more parameters, there are other, more technical web-based flight time calculators. We recommend:
If you would like to learn more about how to achieve a longer flight time, then a good place to start is our previous blog post - efficiency vs. performance.