How this instrument works
Multirotor flight time comes down to a simple trade: how much energy the battery holds versus how fast the motors burn through it to keep the aircraft in the air. Energy is capacity (in amp-hours) times voltage, but not all of a LiPo's rated capacity is usable — discharging a pack all the way to empty damages it, so most pilots plan around 80% usable capacity and leave the rest as a safety margin.
Power draw is estimated from the drone's all-up weight (AUW) — everything that leaves the ground, battery included — multiplied by a power-per-kilogram figure that captures how efficiently the motors and props convert electrical power into lift. A commonly used conservative baseline is around 170 watts per kilogram for hover; more efficient prop-and-motor combinations can draw meaningfully less. Dividing that hover power by voltage gives the average current draw, and dividing usable capacity by that current draw gives flight time.
This estimates hover-only flight time under steady, level flight — the number printed on a spec sheet, not what a stopwatch shows during an actual flight. Aggressive maneuvering, wind, cold temperatures, and payload beyond the base AUW all pull current higher than the hover estimate, so real-world flights typically run shorter than this figure, sometimes considerably so for racing or freestyle flying.
- Enter the battery's capacity in amp-hours (a 5000 mAh pack is entered as 5).
- Set the usable discharge percentage — 80% is a common safe target for LiPo packs.
- Enter the battery's voltage (e.g. 11.1 V for 3S, 14.8 V for 4S, 22.2 V for 6S).
- Enter the drone's all-up weight in kilograms — frame, battery, props, and any payload combined.
- Enter the estimated hover power requirement in watts per kilogram; 170 is a reasonable conservative default.
- Read the estimated flight time in hours and minutes.
Worked example — a mid-size 6S quadcopter
A quadcopter with a 5 Ah (5000 mAh), 6S (22.2 V) battery, discharged to 80% usable capacity, weighs 1.5 kg all-up and is estimated at a conservative 170 W/kg hover power requirement. Average amp draw comes first: AAD = (1.5 × 170) ÷ 22.2 = 11.486 A.
Flight time follows from usable capacity divided by that draw: (5 × 0.80) ÷ 11.486 = 0.3482 hours, or about 20.9 minutes. That's the hover-only estimate — steady, level flight with no wind and no aggressive maneuvering — so a pilot actively flying acro or fighting a breeze should expect noticeably less time in the air than this figure.
Questions
Why does this calculator ask for watts per kilogram instead of motor specs?
Because a full power calculation needs motor KV, prop pitch and diameter, ESC efficiency, and more — data most pilots don't have on hand. Watts-per-kilogram is a simplified stand-in that folds all of that into one efficiency number, commonly estimated around 170 W/kg for a typical hover, letting you get a usable flight-time estimate from just weight and battery specs instead of a full power-system simulation.
Why only discharge the battery to 80% instead of using the full capacity?
LiPo batteries lose capacity and lifespan fast when repeatedly drained close to empty, and voltage sag near full discharge can trigger a low-voltage cutoff mid-flight. Planning around roughly 80% usable capacity keeps a safety margin for the return flight and protects the pack's long-term health — pushing past that limit trades battery life and safety margin for a few extra minutes in the air.
Why is real flight time usually shorter than the calculated estimate?
This formula assumes steady hover at a fixed power draw, but real flights rarely stay that steady — accelerating, climbing, fighting wind, and aggressive maneuvers all pull more current than hover does. Racing and freestyle flying in particular can draw two to three times hover power during hard maneuvers, which is why a hover-time estimate is best treated as an upper bound, not a promise.
Does a heavier battery always mean longer flight time?
Not necessarily — a bigger battery adds capacity, but it also adds weight, which raises the all-up weight and therefore the power needed to hover. Past a certain point, the extra weight of a larger pack cancels out the extra capacity it provides, which is why racing and freestyle builds often use smaller packs than their maximum capacity limit would allow.
How much does voltage (cell count) affect flight time on its own?
Voltage mainly changes current draw, not total energy — a 6S pack delivers the same watt-hours as an equivalent-capacity 3S pack, just at roughly double the voltage and half the current, for the same power output. Higher voltage generally means lower current for the same power, which reduces resistive losses in wiring and ESCs, giving a modest efficiency edge rather than a dramatic flight-time change on its own.