The Wheel Size Gear Ratio Speed Calculator estimates your eBike’s actual riding speed based on motor RPM, gear ratios and total wheel diameter including tire height. Larger wheels increase distance per rotation while higher gear reduction multiplies wheel torque but lowers speed. This tool converts mechanical RPM into real-world km/h.
Wheel size determines how far you travel per wheel rotation. A 29-inch wheel covers more distance each turn than a 20-inch wheel, which is why large diameter wheels usually increase top speed at the same RPM. Tire height adds additional circumference so actual speed often differs from nominal wheel size.
Gear ratio multiplies motor torque at the wheel but reduces output RPM. For example, a 4:1 reduction means the motor turns four times to produce one wheel rotation. Hub motors operate near wheel RPM directly, while mid-drive systems rely heavily on reduction gearing to balance torque and speed.
Tire thickness increases the effective wheel diameter. Off-road tires and fat tires add more rolling circumference, increasing real speed calculation compared to nominal rim size. This is why two 26-inch wheels can produce different travel speeds when one uses taller tire sidewalls.