Engineering calculators
Estimate flight time, check thrust margins, size batteries and plan mapping missions. All calculations run in your browser.
Flight time estimator
Hover endurance from battery energy, all-up weight and propulsion efficiency.
- Estimated hover time
- min
- Hover power
- W
- Hover current
- A
- Usable energy
- Wh
Method and assumptions
P = AUW / η + Pav · I = P / (S × Vavg) · t = (C × u) / I × 60
- η is whole-system hover efficiency in grams per watt. Motor test tables exclude ESC losses and voltage sag, so use lower values than the datasheet.
- Average voltage under load is used: LiPo 3.6 V, LiHV 3.75 V, Li-ion 3.5 V per cell.
- C is capacity in Ah and u is the usable fraction: about 80 % for LiPo, 85 % for Li-ion.
Thrust-to-weight ratio
Check whether a motor and propeller combination has enough reserve for your airframe.
- Thrust-to-weight
- : 1
- Total thrust
- g
- Thrust needed to hover
- % of max
Method and assumptions
TWR = (n × Tmax) / AUW · hover share = AUW / (n × Tmax)
- A multirotor needs at least 2:1 to remain controllable in wind and during manoeuvres.
- Thrust is not linear with throttle, so the hover share is not the same as hover throttle position.
Battery energy and transport
Pack voltage, energy, maximum current and air-travel category for LiPo, LiHV and Li-ion packs.
- Energy
- Wh
- Nominal voltage
- V
- Fully charged
- V
- Storage voltage
- V
- Max continuous current
- A
Method and assumptions
Wh = S × Vnom × Ah · Imax = C × Ah
- Cell voltages used: LiPo 3.7 / 4.2 / 3.8 V, LiHV 3.8 / 4.35 / 3.85 V, Li-ion 3.6 / 4.2 / 3.7 V (nominal / full / storage).
- Air transport limits follow IATA guidance for passengers; the Wh value printed on the battery label applies. Always confirm with your airline.
Motor RPM and propeller tip speed
Estimate rotational speed and blade tip velocity to keep the propeller in an efficient range.
- Tip speed (loaded)
- m/s
- Tip Mach number
- M
- No-load RPM
- RPM
- Loaded RPM
- RPM
Method and assumptions
RPM = KV × S × Vfull × k · vtip = π × D × RPM / 60 · M = vtip / 343
- Full-pack voltage is used because tip speed peaks on a fresh battery.
- Speed of sound taken as 343 m/s at 20 °C. Small FPV propellers commonly run at Mach 0.6 to 0.8 at full throttle.
Ground sampling distance
Image resolution on the ground and single-frame footprint for photogrammetry planning.
- GSD
- cm/px
- Footprint width
- m
- Footprint height
- m
- Area per image
- ha
Method and assumptions
GSD = (Sw × H × 100) / (f × Wpx) · footprint = GSD × pixels / 100
- Assumes a nadir (straight-down) camera over flat terrain.
- Use the real focal length, not the 35 mm equivalent.
Results are engineering estimates based on the stated formulas and typical values. Real performance depends on airframe drag, temperature, battery condition and flying style. Validate with bench tests and manufacturer data before flight.