This Motor Power & Speed Calculator estimates the realistic maximum speed your eBike can achieve using motor wattage, rider weight, aerodynamics, wheel diameter, and road gradient. Instead of simple linear formulas, it uses a physics-based power balance model that considers aerodynamic drag, rolling resistance, gravitational force, and drivetrain efficiency.
How the Motor Power & Speed Calculator Works
Your eBike’s top speed is determined when the motor's available power equals the forces opposing motion:
- Aerodynamic drag force (dominant after 25 km/h)
- Rolling resistance
- Gravity (if riding uphill)
- Mechanical + motor losses (efficiency)
When the required power to maintain a given speed equals the motor’s effective power output, that speed becomes the theoretical maximum.
Typical Real-World Speed Examples
- 250 W motor: 22–28 km/h (14–17 mph)
- 500 W motor: 32–38 km/h (20–24 mph)
- 750 W motor: 40–45 km/h (25–28 mph)
- 1000 W motor: 48–55 km/h (30–34 mph)
Factors That Affect Speed
- Riding posture (CdA changes speed by ±20%)
- Rider + bike weight
- Wheel size + tire width
- Motor efficiency
- Wind direction
- Road incline
Tip: A tucked riding position reduces drag dramatically and can increase top speed by 4–7 km/h.
Frequently Asked Questions
Q: Why does my eBike not reach the motor's theoretical speed?
A: Real-world speed is limited by drag, weight, controller limits, wind, temperature, and battery voltage sag.
Q: Is a higher power motor always faster?
A: Mostly yes, but speed also depends heavily on aerodynamics. At high speeds, most power fights air resistance.
Q: Do wheel size and tire width affect speed?
A: Yes. Larger wheels increase effective speed per motor RPM, while wide tires create more drag.
Q: Why is uphill speed much slower?
A: Uphill climbs add gravitational resistance, requiring significantly more power to maintain speed.
