RC car calculators

Researched from manufacturer specs and verified owner reviews. Updated 2026.

Quick answer

Eight calculators, each showing its formula. The most used is the gear ratio and top speed calculator: motor KV x volts / final drive ratio x tire circumference gives the speed ceiling, and real cars reach about 80 to 90 percent of it.

Put the numbers to work

ARRMA 1/10 Granite 4X4 223S BLX BRUSHLESS RC Monster Truck RTR

1/10
4WD
Brushless

A 3S-capable brushless 4x4: the calculators on this site are built around trucks like this one.

$339.11 listed price, changes often

Check price on Amazon Full specs

Gear ratio and top speed calculatorWork out your RC car final drive ratio and top speed from motor KV, LiPo cell count, pinion, spur, internal transmission ratio and tire size. Formula shown.Motor KV and RPM calculatorMotor KV times voltage gives RPM. Enter KV and LiPo cell count to get nominal and full-charge RPM, and the speed ceiling for your gearing and tire size.LiPo runtime calculatorHow long will your RC car battery last? Enter pack capacity in mAh and average current draw to get runtime in minutes, with hard-bashing and cruising estimates.Cell count, voltage and C rating calculatorConvert LiPo cell count to voltage (nominal, full, storage, cutoff) and C rating to maximum continuous current. For RC car packs from 2S to 8S.Charge time calculatorHow long does an RC car battery take to charge? Enter capacity, charger amps and how drained the pack is to get charge time and the C rate you are charging at.Pinion and spur swap calculatorSee what a new pinion or spur does before you buy it: percent change in top speed and final drive, new speed, and a motor temperature risk rating.RC scale converterConvert between RC scales, work out the real-world size a model represents, and turn RC speed into scale speed, the full-size equivalent.Right RC car for an ageEnter a child’s age, experience and where they will drive to get toy grade or hobby grade, a sensible top speed, scale and battery type, with picks for that age.

Which calculator do I need?

Changing gears or buying a pinion: pinion and spur swap, then top speed.
Choosing a motor or moving from 2S to 3S: KV and RPM.
Buying batteries: runtime, voltage and C rating and charge time.
Buying for a child: the age calculator.

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RCCarCalc is researched guidance, not professional advice. Figures come from published manufacturer specifications, listings and verified owner reports, not hands-on testing. Speeds are theoretical or as listed; real results depend on gearing, battery, tires and terrain. See how we research.