Why this site exists
Electric scooter specifications are unusually unreliable. Range is measured at a speed nobody rides, motor power is quoted as a peak figure the motor cannot hold, and battery capacity is sometimes multiplied by charge voltage instead of nominal voltage to make the watt-hour number bigger. None of that is illegal. All of it makes buying decisions harder than they should be.
The calculators here take the opposite approach: state the model, expose the coefficients, and let the result be whatever the physics says — including when that is disappointing.
The performance model
Range, top speed and hill climbing all come from the same three forces, which is standard vehicle dynamics rather than anything novel:
- Rolling resistance: Crr × m × g × cos θ — scales with weight, dominant at low speed.
- Aerodynamic drag: ½ × ρ × CdA × v² — scales with the square of speed, dominant above about 20 km/h.
- Gradient: m × g × sin θ — the biggest single term on any real hill.
Multiply the total force by speed for power at the wheel, divide by drivetrain efficiency for power at the battery, and everything else follows. Solving the reverse problem — what speed a given power sustains — has no closed form, so the tools bracket the answer and bisect until both sides balance.
Where the constants come from
The coefficients are the part most calculators get wrong, usually by borrowing bicycle figures. Scooters are not bicycles:
| Constant | Value | Reasoning |
|---|---|---|
| Drag area, standing rider | 0.72 m² | Upright rider is roughly a small door; a bicycle tuck is nearer 0.35 |
| Drag area, tucked | 0.58 m² | Crouched over the bars at speed |
| Rolling resistance, city asphalt | 0.018 | 8.5–10″ pneumatic tyres; small wheels deform more per revolution than bicycle tyres at 0.008 |
| Rolling resistance, solid tyres | 0.030 | Airless tyres trade puncture resistance for range |
| Drivetrain efficiency, cruise | 75% | Hub motor plus controller at moderate load |
| Drivetrain efficiency, climbing | 72% | Hub motors are least efficient at low RPM and high torque |
| Accessory draw | 8 W | Lights, controller and display idle consumption |
| Usable battery capacity | 90% | BMS reserves headroom at both ends of the voltage range |
| Air density | 1.225 kg/m³ | 15 °C at sea level |
These defaults are calibrated so that the range model reproduces measured consumption for popular scooters — a Ninebot Max G30 riding steadily at 20 km/h lands near 12 Wh/km and around 42 km of range, which matches what owners report. Every one of them is an input you can change.
The battery and electrical models
Charge time follows real constant-current / constant-voltage behaviour: bulk charging to roughly 80% state of charge, then a taper in which average current falls to about 45% of the bulk figure. That is why the last fifth of a charge takes as long as the first four.
Degradation is split into cycle ageing and calendar ageing, because they have different causes and different remedies. Wire sizing applies two independent constraints — voltage drop over the round-trip length, and the conductor's own thermal rating with a 25% margin — since either can decide the answer and ignoring the thermal one is how looms melt.
What these tools deliberately do not do
- Model wind. A headwind adds to your effective speed in the drag term; no calculator can guess it.
- Guess your tyre pressure. Running 35 psi instead of 50 psi can add a third to rolling resistance.
- Include total cost of ownership. Insurance, depreciation and repairs vary too much by market to average honestly.
- Include battery manufacturing carbon. The emissions tools report operational figures and say so.
- Replace an engineer. These are planning estimates. For anything safety-critical, verify against the component datasheets.
Privacy, in one paragraph
Everything runs in your browser. Nothing you type is transmitted, because there is no server to transmit it to — the site is static files. Tools remember your last inputs in your own browser's local storage so you do not have to retype them, and clearing site data removes that. There is no account, no email capture and no advertising.
Corrections
If a coefficient looks wrong, or a result disagrees with something you have measured, that is worth knowing — measured data beats a default every time. Email hello@mrscooty.com with the numbers and how you got them.