Battery Current & Capacity Calculator

Calculate key usage specifications for your LiPo battery based on capacity, voltage, discharge rate and recharge rate.

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Results

Watt Hours (Wh) -
Total energy stored in the battery. Calculated as capacity (Ah) × voltage.
Amp Hours (Ah) -
Battery capacity in amp hours. Calculated as capacity (mAh) ÷ 1000.
Discharge Current (A) -
Maximum safe continuous discharge current. Calculated as capacity (Ah) × C-rating.
Charge Current (A) -
Recommended charge current. Calculated as capacity (Ah) × Charge C-rating.

Usage Guide

Battery C-Rating Calculator

Calculate the real C-rating of your battery based on measured internal resistance and capacity.

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Results

C Rating -
The battery's discharge capability rating. Calculated as 2500 ÷ √(IR × capacity).
Max Current (A) -
Theoretical maximum safe continuous discharge current. Calculated as √(6 × (capacity ÷ IR)).
Figure of Merit (FOM) -

Overall battery performance metric combining capacity and internal resistance. Higher is better. Calculated as 12000 ÷ (IR × capacity).

Purpose: FOM provides a normalized, dimensionless metric for comparing battery performance across different sizes and chemistries—allowing you to objectively compare a 5000mAh 4S pack against a 3000mAh 6S pack, for example.

Typical ranges: <0.8 (poor/worn), 0.8-1.0 (average hobby grade), 1.0-1.5 (good quality), 1.5-2.0 (premium), >2.0 (exceptional/competition grade).

Usage Guide

Gear Size Calculator

Calculate gear specifications. Edit any field and others will update automatically. Lock a section to keep it constant.

Teeth
Unlocked
Please enter number of teeth
Pitch
Unlocked
Please enter at least one pitch value
Diameter
Unlocked
Please enter at least one diameter value

Usage Guide

Gear Ratio Calculator

Calculate individual and overall gear ratios for your RC drivetrain configuration.

Vehicle Presets

Motor/Engine

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Motor Ratio: -.---:1

Transmission

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Transmission Ratio: -.---:1

Center Differential

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Center Diff Ratio: -.---:1

Rear Differential

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Rear Diff Ratio: -.---:1

Front Differential

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Front Diff Ratio: -.---:1

Overall Ratios

Overall Rear Ratio -.---:1
Total gear reduction from motor to rear wheels. Multiply all ratios in the rear drivetrain path.
Overall Front Ratio -.---:1
Total gear reduction from motor to front wheels. Multiply all ratios in the front drivetrain path.

Usage Guide

Speed Calculator

Calculate your RC vehicle's top speed from motor specs, gearing, and tire size, with realistic modeling of aerodynamic drag and rolling resistance.

Motor & Electrical

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Must be between 0 and 100

Gear Ratio

Please enter a valid positive integer
Please enter a valid positive integer
Gear Ratio -
Please enter a valid positive number
For complex drivetrains, see Gear Ratio Calculator →
Please enter a valid positive number
Measure loaded diameter (tire under vehicle weight)

Results

Motor RPM -
Motor shaft revolutions per minute. Calculated as KV × Voltage × (Efficiency / 100).
Wheel RPM -
Wheel revolutions per minute after gear reduction.
Speed Reduction -
-
Maximum Power Available -
Total electrical power the system can deliver based on ESC current limit and battery voltage. W (watts) is the unit of power.
Calculated as ESC Current (A) × Battery Voltage (V) × Number of Motors × (Efficiency / 100)
Power-to-Weight Ratio -
Vehicle performance metric indicating acceleration potential. Higher W/kg = better acceleration.
Calculated as Power (W) ÷ Weight (kg)
Theoretical Top Speed (No Load) -
Maximum speed assuming no aerodynamic drag or friction losses. Calculated as (Wheel RPM × π × Tire Diameter × 60) / 1,000,000 for km/h.
Realistic Top Speed (With Losses) -
Estimated real-world top speed accounting for aerodynamic drag and rolling resistance.
Iteratively calculated: start from theoretical speed, reduce in steps until (Rolling Force + Drag Force) at that speed is sustainable by available power
Rolling Resistance Force -
Force from tire/surface friction resisting motion. N (newtons) is the SI unit of force. lbf (pound-force) is the imperial equivalent. Calculated as (mass × 9.81) × Crr.
Aerodynamic Drag Force -
Air resistance force at theoretical top speed. N (newtons) measures force in SI units. lbf (pound-force) is the imperial unit. Increases with the square of velocity. Calculated as 0.5 × 1.225 × v² × Area × Cd.
Total Resistance Force -
Combined rolling resistance and aerodynamic drag. N (newtons) and lbf (pound-force) measure the total force opposing motion.
Calculated as Rolling Force + Drag Force

Usage Guide

Resistor Load Bank Designer Calculator

Calculate parallel and series configurations for resistor load banks with voltage and wattage analysis.

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Please enter a valid positive number
Please enter a valid positive number
Peak (max charge) cell voltage

Parallel vs Series Performance

Parallel

Ohms (Ω): -
Watts (W): -

Series

Ohms (Ω): -
Watts (W): -

Voltage Table

Configuration Parallel Series
Cells Voltage Theoretical Amps Watts Max Amps Theoretical Amps Watts Max Amps

Parallel Configuration

Cells V T.A W Max A

Series Configuration

Cells V T.A W Max A

Usage Guide

About Calc Labs

Our Mission

Calc Labs exists on a simple principle: mathematics should be open, accessible, and free. The formulas that govern battery performance, gear ratios, and electrical systems aren't proprietary secrets—they're fundamental physics available to everyone. We believe that understanding the technical aspects of your RC hobby shouldn't require expensive software or proprietary tools.

Why This Exists

Too often, hobbyists rely on manufacturer specifications that are inflated for marketing purposes, or make critical decisions based on guesswork. This site provides evidence-based calculations grounded in electrical engineering principles and empirical testing. Whether you're selecting a battery, tuning your drivetrain, or designing a load bank, these tools give you accurate, actionable data.

Our Ethos

Transparency: All formulas and constants are explained. No black boxes, no hidden calculations. You should understand not just the results, but why they matter.

Accuracy over Marketing: We acknowledge when manufacturer specs are unreliable (looking at you, C-ratings) and provide methods to measure real-world performance.

Education: Every calculator includes usage guides explaining the underlying concepts. Understanding the math makes you a better hobbyist.

Community-Driven: This is a living project. If you find errors, have suggestions, or want to contribute calculators for new applications, we want to hear from you, please contact us with your feedback.

Technical Approach

Our calculations balance theoretical accuracy with practical usability. We use empirically-derived constants calibrated for hobby-grade components, acknowledge real-world limitations like temperature effects and manufacturing variance, and always recommend safety margins. Math is precise, but batteries and motors are not—our tools reflect that reality.

Open Philosophy

Knowledge grows when it's shared. All calculations on this site use standard formulas from electrical engineering and mechanical design. We don't claim ownership of physics—we just make it easier to apply. This site is built with simple, accessible web technologies because tools this useful shouldn't require complex infrastructure or vendor lock-in.

Looking Forward

Calc Labs is continuously evolving. We're adding new calculators, refining existing formulas based on user feedback, and expanding educational content. The goal is to become the definitive technical reference for RC hobbyists who value precision over guesswork.

Built by hobbyists, for hobbyists. Because math doesn't need a marketing budget.


Disclaimer

The calculators and information provided on Calc Labs are for reference purposes only. While we strive for accuracy, real-world results may vary due to factors beyond our control, such as component tolerances, environmental conditions, and user application. Always verify calculations with practical testing and consider safety margins when applying these results to your projects.


Copyright Notice

© 2026 Calc Labs. All rights reserved. The mathematical formulas and educational content are freely shared, but the code implementation may not be copied, modified, or redistributed without explicit permission. All calculators are provided as-is for reference purposes.

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Before You Write

Check the Usage Guide section on each calculator page—many common questions are answered there. If you're reporting a calculation issue, try to include the specific input values you used.


Response Time

Thank you for your feedback! We typically respond to all inquiries within 72 hours as we carefully review each one to ensure the best possible support. Your input truly helps us improve Calc Labs—thanks for being part of making it better!