Basher Motor, ESC & LiPo S-Count Matcher

No single rc car brushless motor size chart fits every truck. Can size and kV come from each manufacturer’s spec sheet, so the reliable check is your own numbers. This matcher compares your motor, ESC and battery spec sheets against each other and shows theoretical no-load RPM.

How to use the Motor, ESC & LiPo S-Count Matcher

Enter limits from your manuals. Results are a spec-sheet comparison, not a safety approval. None of the fields is pre-filled, so every number you see comes from you or from the formula.

1. Motor kV: copy it from the motor manual or spec sheet (RPM per volt).
2. Motor max RPM (optional): enter it only if the motor manufacturer publishes a maximum RPM. If you leave it blank, the RPM check shows “Not checked”.
3. ESC max cell count: the highest LiPo cell count (S) your ESC manual lists.
4. Battery cell count: the S number on your battery label, such as 3S or 6S.
5. Select Check my combo to see the results.

How to read your results

• Theoretical no-load RPM: kV × S × 3.7, rounded to a whole number. It is theoretical, at nominal voltage, with no load on the motor.
• ESC cell count: “Within the ESC limit you entered” when your battery’s S is equal to or below the ESC maximum you typed. “Exceeds the ESC limit you entered” when it is higher.
• Motor RPM: “Within the motor RPM limit you entered” when the theoretical RPM is equal to or below your motor’s stated maximum. “Exceeds the motor RPM limit you entered” when it is higher. “Not checked (no motor max RPM entered)” when you left that field blank.
• Matching roundup: the roundup on this site that matches your battery’s cell count (3S, 4S, 6S or 8S). For any other cell count, the tool says no S-specific roundup exists and points to our brushless monster truck roundup instead.

If anything shows “Exceeds”, the tool flags it in text with a ⚠ icon, so the warning does not rely on color. Re-read the motor and ESC manuals, then ask the manufacturer before you buy or plug anything in. A result inside your entered limits does not mean a combination will work. It means only that the numbers you entered do not exceed the limits you entered.

How the RPM formula works

A brushless motor’s kV rating is its no-load RPM per volt. The Traxxas Slash 4X4 manual puts it this way: “The kV rating equals no-load motor rpm with 1 volt applied.” A LiPo cell has a nominal voltage of 3.7 V, so an S-cell pack is nominally S × 3.7 volts. A 3S pack is 11.1 V nominal, the same figure the Traxxas manual gives. Multiply the two and you get:

Theoretical no-load RPM = motor kV × battery cell count (S) × 3.7

A freshly charged LiPo cell is about 4.2 V, not 3.7 V. Unloaded RPM can therefore be up to about 4.2 ÷ 3.7 ≈ 1.14 times the nominal figure. Keep that headroom in mind when your result sits close to a motor’s stated maximum RPM.

Can I run 6S? Finding size, kV and max S on a spec sheet

Whether you can run 3S, 4S, 6S or 8S depends on the limits your ESC and motor manufacturers state, not on a generic chart. The ESC manual usually lists the supported LiPo cell count, such as “2S–3S LiPo” or “up to 6S”. The highest number in that range is your ESC max S. The motor listing or manual gives the kV and sometimes a maximum RPM. Some motor listings also give a supported cell range. If yours does, treat it as an extra limit and check it yourself, because the tool does not ask for it.

You will often see size codes such as “390 size” or can dimensions in brushless motor listings. Read the size, and which vehicles it fits, from the manufacturer’s own listing. For background on can sizes and kV by scale, see our related guide, RC Brushless Motor Size Chart: Can Sizes and kV by Scale. Then use this matcher to compare the spec-sheet numbers you actually have.

If you are moving from NiMH to LiPo, the same rule applies: check the cell count your ESC manual allows before you choose a pack. Our guide Can You Replace NiMH With LiPo in an RC Car? What to Check First covers that switch.

Methodology & sources

Every number in the results either comes from your manuals or is computed with the formula above, using 3.7 V as the nominal voltage per cell. The tool rounds RPM to the nearest whole number. Both checks are strictly “greater than”, so a value equal to a limit counts as within it. The tool does not model load, gearing, tire size, vehicle weight, temperature, amperage, battery C rating or voltage sag, and it does not check a motor’s supported cell-count range. It does not supply any motor or ESC limits itself. Everything runs in your browser, and nothing you type is stored or sent anywhere.

• Your own motor, ESC and battery spec sheets and labels: the data the tool compares.
• Wikipedia: Lithium polymer battery: 3.6–3.7 V nominal cell voltage, about 4.2 V fully charged.
• Traxxas Slash 4X4 owner’s manual 68386-4: kV definition; 2S = 7.4 V and 3S = 11.1 V nominal.
• Wikipedia: Motor constants: Kv as RPM per volt at no load.
• Battery University BU-409: lithium cells typically charge to 4.20 V/cell.

LiPo batteries and high-power RC systems can cause fire, injury or property damage if mismatched or misused. This tool only compares numbers you enter; always follow the motor, ESC and battery manufacturers’ instructions and warnings.

Last updated: October 2026

FAQ

Can I run 6S in my RC truck?

Only if 6S is within the limits your ESC and motor manufacturers state. This matcher compares battery S with the ESC maximum S you enter and, optionally, theoretical nominal RPM with a motor maximum RPM, but it does not check a motor’s supported cell-count range. It is a spec-sheet comparison, not a safety approval.

What does kV mean on a brushless motor?

kV is the motor’s no-load RPM per volt applied. Traxxas puts it this way: “The kV rating equals no-load motor rpm with 1 volt applied.”

Why is the RPM figure only theoretical?

It multiplies kV by the pack’s nominal voltage (3.7 V per cell) with no load on the motor. Gearing, tires, vehicle weight, heat and voltage sag under load all change real-world RPM, and the tool models none of them.

Why can unloaded RPM be higher than the number shown?

A freshly charged LiPo cell sits at about 4.2 V, not the 3.7 V nominal figure. Unloaded RPM can therefore be up to about 4.2 ÷ 3.7 ≈ 1.14 times the nominal result.

Does this tool include a brushless motor size chart?

No. Motor can sizes and kV ranges vary by manufacturer, so read the size and kV from the manufacturer’s own listing or manual, then enter the numbers here.

Related guides

• RC Brushless Motor Size Chart: Can Sizes and kV by Scale
• Types of RC Cars: Trucks, Buggies, Crawlers, Drifters and More
• Short Course Truck vs Stadium Truck: Which RC Racer Suits You?
• Can You Replace NiMH With LiPo in an RC Car? What to Check First
• RC Buggy vs Short Course Truck: Handling, Speed and Durability
• Types of RC Racing Classes: Buggy, Truck, Touring and Oval