RC Tools

Gear Calculator

Pinion, spur, internal ratio, motor KV, and tire size → final drive ratio, top speed, wheel RPM, and rollout. All math runs in your browser — nothing is saved or sent.

Inputs
Crawlers ~1000–3000 · Bashers ~3000–6500 · Speed 7000+
Motor gear
Main gear
Diff + drivetrain
Common: SCX10 II / TRX-4 = 2.92 · Capra = 2.72 · Wraith = 2.57 · Enduro = 2.56 · SCX24 = 9.0
1.9" crawler ~96–108 mm · 2.2" ~110–115 mm · 1/8 buggy ~100–115 mm
85% is a safe default. Lower for worn or open diffs.
Results
  • Motor RPM (no-load)
    —
  • Final drive ratio
    —
  • Wheel RPM
    —
  • Rollout (mm / motor rev)
    —
  • Top speed (km/h)
    —
  • Top speed (mph)
    —
    • Adjust any input — results update instantly.
    Note. Top speed is theoretical at full throttle / no-load. Real-world is typically 70–85% of this due to terrain, tire slip, battery sag, and ESC limits. Use this to compare setups, not as an absolute number.
    Compare two gear setups

    Inherits motor RPM, internal ratio, tire, and efficiency from above. Only adjust pinion and spur here.

    Setup A
    Speed: —   FDR: —
    Setup B
    Speed: —   FDR: —
    Fill in the main form first.
    Common internal drivetrain ratios Show ▾