What is e-bike range and why does it matter?
E-bike range is the total distance you can ride on a single battery charge. It depends on far more than just battery size. Real-world range is shaped by a combination of physics forces: rolling resistance from tires on pavement, aerodynamic drag from wind and speed, grade resistance from hills, and how much the motor assists versus how much the rider pedals.
Manufacturers often quote optimistic range figures based on ideal conditions: flat terrain, low speed, eco assist mode, and a lightweight rider. In practice, most riders see 30-60% less range than advertised. This estimator uses physics-based calculations to give you a realistic picture of how far your battery will take you under your actual riding conditions.
Understanding your true range helps you plan rides with confidence, avoid running out of battery far from home, and make informed decisions when purchasing an e-bike or replacement battery.
How the calculation works
The estimator models four primary forces that consume battery power:
**Rolling resistance** accounts for the friction between tires and road surface. It depends on total weight (rider plus bike) and tire pressure. Properly inflated tires reduce this force by roughly 33%.
**Aerodynamic drag** is the dominant force at higher speeds. Drag increases with the square of your speed through the air, so riding at 30 km/h requires four times the aero power of 15 km/h. Headwind adds to your effective air speed, dramatically increasing drag.
**Grade resistance** represents the energy needed to climb hills. On hilly terrain, you expend significant energy going uphill, but recover some through coasting downhill. The calculator accounts for this partial recovery.
**Formula:** \`\`\` Total Power = Rolling Resistance + Aero Drag + Grade Resistance + Accessories Range = (Battery Capacity / Motor Power Draw) x Speed \`\`\`
The motor's share of total power depends on the assist level. In Eco mode, the motor provides about 50% of the effort. In Turbo mode, it handles roughly 95%. Higher assist means faster battery drain but less physical effort from the rider.
Key factors that affect e-bike range
- **Battery capacity (Wh)**: The single biggest factor. A 500 Wh battery stores twice the energy of a 250 Wh battery. Common sizes range from 250 Wh on compact bikes to 1000+ Wh on cargo or dual-battery setups. - **Speed**: Aerodynamic drag increases with the square of speed. Slowing from 30 km/h to 20 km/h can increase range by 40-60%. - **Terrain**: Flat routes use the least energy. Hilly terrain can cut range by 30-50% compared to flat ground. Mountainous routes with sustained climbs have the greatest impact. - **Assist level**: Eco mode can double or triple your range compared to Turbo mode. The tradeoff is more physical effort from the rider. - **Rider and bike weight**: Heavier loads increase both rolling resistance and climbing effort. Every extra 10 kg reduces range by roughly 3-5% on flat ground and more on hills. - **Wind**: A moderate headwind of 16 km/h can reduce range by 15-25%. Riding with a tailwind has the opposite effect. - **Tire pressure**: Underinflated tires increase rolling resistance by about 50%, reducing range noticeably on long rides. - **Temperature**: While not modeled in this calculator, cold weather (below 5C) can reduce battery capacity by 10-20%.
How to use
1. Select your preferred units for distance (km or miles) and weight (kg or lbs) 2. Enter your battery capacity in watt-hours, or select a common size from the quick-pick buttons 3. Enter your body weight and the weight of your e-bike (including battery) 4. Set your average cruising speed using the slider 5. Choose your terrain type: flat, hilly, or mountainous 6. Select your pedal assist level: Eco, Tour, Sport, or Turbo 7. Set headwind conditions and tire inflation status 8. View your estimated range, riding time, and detailed power breakdown instantly
Tips to maximize your e-bike range
- **Use Eco or Tour mode** for commuting and casual rides. Save Sport and Turbo for steep hills. - **Keep tires inflated** to the recommended pressure printed on the tire sidewall. Check weekly. - **Reduce speed slightly** on long rides. Dropping from 28 km/h to 22 km/h can add 20-30% more range. - **Plan routes with fewer hills** when range is a concern. Even small detours around steep climbs can save significant energy. - **Pedal actively** rather than relying entirely on the motor. Your legs are a free power source. - **Minimize stop-and-go** riding. Accelerating from a stop consumes far more energy than maintaining a steady speed. - **Store the battery indoors** during cold weather. A warm battery holds more charge and delivers better performance.
FAQs
Q: How accurate is this e-bike range estimator? A: The estimator uses established physics formulas for rolling resistance, aerodynamic drag, and grade resistance. It provides a realistic estimate under the specified conditions. Actual range may vary by 10-20% depending on factors like road surface quality, wind gusts, elevation changes, temperature, and riding style. It is more accurate than manufacturer claims, which are typically measured under ideal conditions.
Q: What battery capacity do I need for my commute? A: As a rule of thumb, plan for about 10-15 Wh per kilometer on flat terrain with moderate assist, or 15-25 Wh per kilometer on hilly terrain. For a 20 km commute on mixed terrain, a 400-500 Wh battery provides comfortable range with margin to spare.
Q: Does rider weight really affect e-bike range? A: Yes. Heavier riders increase both rolling resistance and the energy needed to climb hills. A 100 kg rider will see roughly 10-15% less range than a 70 kg rider under identical conditions on hilly terrain. On flat ground, the difference is smaller (about 5-8%) since aerodynamic drag dominates.
Q: What is the difference between Eco and Turbo assist modes? A: In Eco mode, the motor provides about 50% of the total power needed, with the rider supplying the rest through pedaling. In Turbo mode, the motor handles roughly 95% of the effort. Turbo mode can reduce range by 50-70% compared to Eco, but requires much less physical effort from the rider.
Q: How does headwind affect e-bike range? A: Headwind has a dramatic effect because aerodynamic drag increases with the square of air speed. A moderate 16 km/h headwind effectively doubles the drag at 20 km/h cruising speed, reducing range by 15-25%. Strong headwinds can cut range by 30-40%.
Q: Can I extend my range with a second battery? A: Yes. Many e-bike systems support dual batteries or range extenders. Simply add both battery capacities together when using this estimator. For example, two 500 Wh batteries give you 1000 Wh of total capacity.
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