Aviation Calcs

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Drone Flight Time Calculator

A hovering multirotor holds its weight with n rotors and spends most of its battery on induced power. This page uses actuator-disk theory for that hover power, divides by a figure of merit, adds optional avionics load, and turns usable battery energy into an endurance. If you enter a maximum thrust it also reports thrust-to-weight. It is a hover estimate, not a cruise range or a manufacturer flight-time rating.

Diameter is one rotor (not the tip-to-tip span of the frame). Figure of merit defaults to 0.60, a typical small-quad value; usable battery defaults to 80% of the nominal watt-hours. Capacity may be entered as watt-hours or as mAh and pack voltage.

Result

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Hover endurance is usable energy over hover power

Each rotor carries T/n of the weight. Actuator-disk theory gives an induced velocity vi = √(Ti / (2 ρ A)) and an ideal hover power Pideal = n Ti vi = T √(T / (2 ρ n A)). The shaft (or electrical, at the motors) power is that ideal power divided by a figure of merit FM, plus any avionics load you enter. Endurance is usable battery watt-hours times 3,600, divided by that power. A 2 kg quad on four 0.25 m rotors, FM = 0.60, and 80 Wh usable typically hovers for on the order of tens of minutes at a few hundred watts — a sanity check, not a sales-sheet number.

Forward flight, a climbing profile, wind, battery sag, and motor or ESC efficiency away from the hover point all change the real time. If you care about rotor disk power or a hover ceiling rather than a battery, see the hover power calculator; for a larger electric airplane, see electric aircraft endurance.

Sources

Frequently asked questions

Why is hover time shorter than the time printed on the box?

Manufacturer ratings often include a lighter aircraft, a partial throttle cruise, or a larger usable fraction than 80%. This page is a hover, at the weight you type.

What figure of merit should I use?

Small consumer quads often sit around 0.5–0.7. A 0.60 default is a middle value, not a measurement of your props.

Does this include reserve or a landing battery margin?

Only through the usable fraction. Tighten it if you want a reserve built in.