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Axle Ratio Calculator

The Axle Ratio Calculator computes the rear axle gear ratio from ring gear and pinion gear tooth counts. Determine how your axle ratio affects acceleration, towing capacity, fuel economy, and top speed for trucks and performance vehicles.

Axle Ratio Calculator — Live Preview
Axle Ratio
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Proportion Solver
A : B = C : D — Enter any 3 values
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Results
Visual ratio breakdown
Solved Proportion
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Simplified
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Percentages
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Decimal
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Fraction
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Visual Ratio
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    Ratio Simplifier
    Reduce any ratio to its simplest form
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    Simplified Result
    Reduced to lowest terms
    Simplified Ratio
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    GCD Used
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    Percentages
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    Decimal Ratio
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    Fraction
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    Visual Ratio
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      Ratio Scaler
      Multiply a ratio by a scale factor
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      Scaled Result
      Ratio after scaling
      Scaled Ratio
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      Original
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      Factor
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      Percentages
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      Simplified
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      Visual Ratio
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        What is Axle Ratio?

        Axle ratio (also called rear-end ratio or differential ratio) is the number of times the driveshaft rotates for each rotation of the axle (wheel). A 3.73:1 axle ratio means the driveshaft spins 3.73 times for every one wheel revolution. Higher ratios provide more torque multiplication at the wheels.

        Truck owners choose higher ratios (3.73, 4.10) for towing and acceleration. Highway cruisers prefer lower ratios (3.08, 3.23) for better fuel economy at speed. The axle ratio is determined by the number of teeth on the ring gear divided by the pinion gear teeth.

        Formulas & Equations Used

        This Axle Ratio Calculator uses the following core equations:

        1 Axle Ratio Calculation ▼
        Axle Ratio = Ring Gear Teeth / Pinion Gear Teeth

        A ring gear with 41 teeth and pinion with 11 teeth: Axle Ratio = 41/11 = 3.73:1.

        2 Engine RPM at Speed ▼
        RPM = (Speed × Axle Ratio × Trans Ratio × 336) / Tire Diameter

        At 60 mph, 3.73 axle, 0.70 overdrive, 28-inch tires: RPM = (60 × 3.73 × 0.70 × 336) / 28 = 1878 RPM.

        3 Effective Ratio (with Transmission) ▼
        Effective Ratio = Axle Ratio × Transmission Gear Ratio

        3.73 axle × 2.97 first gear = 11.08:1 overall ratio in first gear.

        How to Use This Axle Ratio Calculator

        Follow these 3 simple steps:

        1

        Enter Your Values

        Type the known values into the input fields above. The Axle Ratio Calculator accepts any positive numbers.

        2

        Choose Calculation Mode

        Select Solve, Simplify, or Scale mode in the calculator. Each applies different equations to your inputs.

        3

        View Results

        Click Calculate to see your answer with a visual ratio bar, pie chart, and step-by-step solution breakdown.

        Example Problems & Step-by-Step Solutions

        Here are 3 worked examples using this Axle Ratio Calculator:

        Example 1 Ring gear: 41 teeth, Pinion: 11 teeth
        1 Axle Ratio = 41 / 11
        2 Axle Ratio = 3.727:1
        3 Commonly rounded to 3.73:1
        ✓ Axle ratio is 3.73:1
        Example 2 Compare 3.23 vs 3.73 for towing
        1 At 3.23: Less torque multiplication, better highway MPG
        2 At 3.73: 15% more torque at wheels, better acceleration
        3 3.73 pulls grades with less strain on the engine
        ✓ 3.73 is better for towing; 3.23 for highway cruising
        Example 3 Engine RPM at 70 mph with 3.55 ratio, 30-inch tires, 0.65 OD
        1 RPM = (70 × 3.55 × 0.65 × 336) / 30
        2 RPM = (70 × 3.55 × 0.65 × 336) / 30
        3 RPM = 54,275.4 / 30 = 1809 RPM
        ✓ Engine turns 1,809 RPM at 70 mph

        Frequently Asked Questions

        What axle ratio is best for towing? ▼

        For heavy towing (7,000+ lbs), use 3.73:1 or 4.10:1. These ratios multiply engine torque more, making it easier to pull heavy loads and climb hills. The tradeoff is slightly lower highway fuel economy.

        How does axle ratio affect fuel economy? ▼

        Lower numerical ratios (3.08, 3.23) improve highway fuel economy because the engine turns fewer RPM at cruising speed. Higher ratios (3.73, 4.10) increase RPM at the same speed, consuming more fuel.

        How do I determine my vehicle's axle ratio? ▼

        Check the door jamb sticker, owner's manual, or RPO code. Alternatively, jack up one wheel, rotate it two full turns, and count driveshaft rotations. If the driveshaft turns 3.73 times, you have a 3.73 ratio.

        Can I change my axle ratio? ▼

        Yes. Swapping the ring and pinion gear set changes the axle ratio. Common swaps include 3.08 to 3.73 for towing, or 3.55 to 4.10 for off-road trucks. Professional installation and setup is recommended.

        What is a limited-slip differential? ▼

        A limited-slip differential (LSD) distributes torque between both wheels when one loses traction, unlike an open differential which sends all power to the spinning wheel. The axle ratio remains the same regardless of differential type.

        Learn About Ratios

        What is a ratio?

        A ratio is a comparison between two or more quantities showing the relative size of one to another. Written as A : B, it means 'for every A units of the first quantity, there are B units of the second.' For example, a ratio of 3 : 4 means for every 3 parts of A, there are 4 parts of B. Ratios are used in cooking, construction, finance, science, and everyday life.

        How do I solve a proportion?

        A proportion is an equation that says two ratios are equal: A : B = C : D. To solve for a missing value, use cross-multiplication. If D is unknown: D = (B × C) / A. This works because in equal ratios, the cross products are always equal: A × D = B × C. Our Proportion Solver does this automatically — just enter any 3 values and it finds the 4th.

        How do I simplify a ratio?

        To simplify a ratio, find the Greatest Common Divisor (GCD) of both numbers and divide each by it. For example, 24 : 36 — the GCD of 24 and 36 is 12. So 24 ÷ 12 = 2 and 36 ÷ 12 = 3, giving the simplified ratio 2 : 3. Our Simplifier automatically finds the GCD and reduces your ratio to its lowest terms.

        What is ratio scaling and when is it useful?

        Scaling a ratio means multiplying both parts by the same factor to create an equivalent, larger (or smaller) ratio. For instance, scaling 2 : 5 by a factor of 3 gives 6 : 15. This is extremely useful for recipes (tripling a recipe), construction (scaling blueprints), mixing solutions, or any scenario where you need to maintain the same proportion at a different magnitude.

        What's the difference between a ratio and a fraction?

        A ratio A : B compares two quantities to each other (part-to-part), while a fraction A/B typically represents a part-to-whole relationship. However, any ratio can be expressed as a fraction: 3 : 4 is equivalent to 3/4 = 0.75. The key difference is context — ratios compare quantities side-by-side, while fractions represent a portion of a total.