Tools
Flight time estimate
Usable capacity divided by average current. The division is trivial. The average is the problem, and this page is mostly about that.
Every flight time calculator does the same arithmetic. What separates a useful estimate from a number that flatters you is the current figure, and almost nobody has a real one.
Why average current is the hard part
A quadcopter's draw is not steady. Hovering, a 5 inch build might sit at a modest current. The same build in a hard climb can pull many times that for a second or two. A freestyle flight is mostly the second thing punctuated by the first, while a long range cruise is almost entirely the first.
That means "average current" is not a property of the aircraft. It is a property of how you fly it. Two pilots with identical hardware land at different voltages after the same number of minutes, and neither of them is doing anything wrong.
The honest way to get the figure is to fly the build once and read it back: a blackbox log records current over the whole flight, and most OSD configurations show consumed capacity in mAh. Divide consumed mAh by flight time and you have a real average for the way you actually fly, which you can then use to plan pack sizes.
- Formulausable mAh / 1000 / amps x 60 = minutes
- Best input sourceblackbox log or OSD mAh consumed
- Worst input sourcea figure from a video about a different build
Why the tool does not offer the whole pack
LiPo packs are not flown flat. Running one down to the point where the flight controller starts complaining costs cycles, and doing it habitually shortens a pack's life considerably. Most pilots plan to land with a reserve, and the tool defaults to four fifths of the printed capacity for that reason rather than because four fifths is a rule.
The option to use the whole pack is there because it is a useful upper bound, not because anyone should fly it. What ageing does to usable capacity, and why a pack that once gave you a comfortable flight now does not, is on the batteries page.
Fly to voltage, not to the clock
A timer tells you how long you have been flying. It does not know that today is colder, that the pack has forty cycles on it, or that you spent the first minute climbing. Voltage under load is what actually tells you when to land, and a pack that sags hard is telling you something a stopwatch cannot.
Capacity is not free
A bigger pack buys minutes and spends them again on the weight it adds. Past a certain size the aircraft is largely carrying battery in order to carry battery, and the curve flattens. Where that point sits depends on the build, which is why this calculator and the thrust to weight calculator are best used together: add the pack weight there, and watch the ratio fall as the estimated time rises.
Long range builds accept a low ratio deliberately to get endurance, which is one of the reasons the 7 inch class exists at all. The frames page covers how size maps to purpose.