How this calculator works
Divide usable battery charge by average flight current. When current is unknown, estimate it from all-up mass multiplied by a measured watts-per-kilogram figure, divided by voltage. The default power density is only an example input: propeller efficiency, wind and flight style change it substantially.
Formula
t = Q x usable fraction / I; I = mass x power per kilogram / voltage.
Worked example
A 5 Ah battery discharged to 80% delivers 4 Ah. At an average 12 A, this supports 1/3 hour, or 20 minutes.
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Frequently asked questions
Does a larger battery always extend flight time?
No. Its extra mass raises the power requirement. Recalculate using the new all-up mass.
Should I use maximum motor current?
Use average current from representative flight logs. Maximum current predicts only a sustained full-throttle case.
Does this predict a safe landing time?
It is a planning estimate. Leave a reserve and follow the aircraft battery warning and operating limits.