SETUP TOOL / RUNTIME + SPEED 2026-11-04
RC runtime & speed calculator
Estimate a run. Check the gearing math. Keep the assumptions visible.
RCCritic is research-led: we use maker data and published sources. We have not done hands-on tests yet.
Real speed is lower. Neither output is a maker claim or a measured result.
5 Ah ÷ 20 A × 60 × 0.8 = 12 min.
3100 × 11.1 × 4 × π × 60 ÷ (10.15 × 63360) ≈ 40.3 mph.
How is RC battery runtime calculated?
Minutes ≈ (capacity_mAh / 1000) / average_current_A × 60 × usable_fraction. The worked example uses a 5000 mAh pack, an assumed 20 A average and an 0.8 usable fraction: 12 minutes.
The 0.8 default reserves capacity as a planning margin. It cannot guarantee a 3.7–3.8 V per cell resting voltage: chemistry, load, temperature and pack condition affect voltage. Follow the battery maker’s storage procedure; the Reedy instructions specify about 3.8 V/cell for storage.
How is theoretical RC speed calculated?
Mph = (kV × volts × tire_diameter_in × π × 60) / (total_gear_ratio × 63360). The equation uses no-load motor speed and tire circumference; it omits tire slip, drivetrain loss, aerodynamic load and voltage sag.
For the assumed 3100 kV, 11.1 V, 4-inch tires and 10.15:1 reduction above, the result is about 40.3 mph. Total gear ratio includes every reduction from motor to wheel; a spur/pinion ratio alone may omit internal gearing.
Can the estimate replace LiPo safety limits?
No. Use a compatible LiPo balance charger and the correct cell setting; never use NiMH mode for a LiPo. Stop at the maker’s low-voltage limit. Damaged or misused LiPo packs can catch fire.
Which sources support this page?
Use the exact model code when checking a maker page. The read date is a record of our research, not a promise that a listing stays unchanged.