What this calculator does
This drone flight time calculator estimates how many minutes a battery pack will last in the air, from its capacity, the drone's average current draw, and a reserve margin kept back for a safe landing. Multirotor drones draw far more current relative to their battery size than most electronics, which is why flight times are measured in minutes rather than hours.
The reserve margin matters because a real flight is never flown to a completely empty battery. Pilots typically land with 15 to 25% of capacity still in reserve, both to protect the battery's lifespan and to leave a safety buffer in case the return leg takes longer than planned. This calculator shows both the full-capacity time and the more realistic time after that reserve is set aside.
The formula
Divide the usable battery capacity (total capacity minus the reserve margin) by the average current the drone draws in flight, which gives the flight time in hours, then convert to minutes. The full-capacity figure, shown alongside it, is the same calculation with no reserve held back, useful for seeing the theoretical ceiling before applying a safety margin.
| Term | Meaning |
|---|---|
| mAh | Milliamp-hours, the standard unit of battery capacity: how much current the battery can supply for one hour. |
| Average current draw | The average current, in milliamps, the drone pulls from the battery across a typical flight, including hover, manoeuvring and payload. |
| Reserve margin | The share of battery capacity deliberately left unused at landing, as a safety and battery-health buffer. |
The inputs explained
| Field | What to enter |
|---|---|
| Battery capacity (mAh) | The battery pack capacity as printed on the battery, in milliamp-hours (mAh). |
| Average current draw in flight (mA) | The average current draw during flight, in milliamps (mA). This is higher during aggressive manoeuvres or with a heavier payload, and lower during gentle hovering. |
| Reserve margin kept unused (safety landing buffer) (%) | The percentage of capacity you plan to keep unused at landing, commonly 15 to 25% for LiPo battery health and safety margin. |
When to use it
Planning a battery swap schedule
Knowing the realistic flight time per battery, after the reserve margin, lets you plan how many packs are needed for a shoot or survey without landing on an empty battery mid-mission.
Comparing battery upgrades
A larger-capacity battery usually adds weight, which raises the average current draw needed to stay airborne. Comparing flight time at the new capacity and the new current draw shows whether the upgrade is actually worth carrying.
Estimating time-of-flight for a mission plan
Before flying a route or survey pattern, working out available flight time against the reserve margin shows how much of the planned route can safely be completed on one battery.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How flight time changes with battery capacity
A fixed average current draw of 20,000 mA, across a range of battery capacities.
| Battery capacity | Estimated flight time |
|---|---|
| 3,000 mAh | 7.2 min |
| 4,000 mAh | 9.6 min |
| 5,000 mAh | 12.0 min |
| 6,000 mAh | 14.4 min |
| 8,000 mAh | 19.2 min |
| 10,000 mAh | 24.0 min |
How flight time changes with current draw
A fixed 5,000 mAh battery, across a range of average current draws.
| Average current draw | Estimated flight time |
|---|---|
| 10,000 mA | 24.0 min |
| 15,000 mA | 16.0 min |
| 20,000 mA | 12.0 min |
| 25,000 mA | 9.6 min |
| 30,000 mA | 8.0 min |
| 40,000 mA | 6.0 min |
Questions
Why is my drone flight time so much shorter than a phone battery of similar capacity?
Drones draw a far higher current relative to their battery capacity than almost any other consumer electronics, because four or more motors are constantly working against gravity. That high current draw is what compresses flight time down to minutes rather than hours.
How is this different from the general battery runtime calculator?
The battery runtime calculator is built for steady, lower-current loads measured in hours, such as a device or backup system. This calculator uses the much higher current draws and shorter timescales typical of multirotor drones, and adds a reserve-margin input tuned to landing safely rather than running a device flat.
Why keep a reserve margin instead of using the full battery?
Repeatedly discharging a LiPo battery close to empty shortens its usable lifespan, and an unexpectedly longer return flight is a common cause of a battery running out before landing. A 15 to 25% reserve covers both risks.
Does payload weight affect this calculation?
Only indirectly, through the average current draw figure. A heavier payload increases the current the motors need to stay airborne, so use a current draw measured or estimated with that payload fitted, rather than the drone's unloaded figure.
For a general battery runtime calculation at lower, steady current draws, see the battery runtime calculator.