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Gear Ratio Calculator

Gear Ratio Calculator


To Calculate:

Input Gear Teeth Number:

Ouput Gear Teeth Number:

Input Rotational Speed:


Input Torque:


Select Transmission:

Engine RPM:

Axle Ratio:

Tire Height (in):

Tire Width (mm):

Wheel Diameter (in):

Aspect Ratio (1-100):


Table of Content

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Use this gear ratio calculator rpm to calculate gear ratio and mechanical advantage that it produces in a mechanical system. Moreover, you could also calculate the system torque, transmission mechanical speed of the tyre along with its diameter. So if you are up to buying a new car, you should have a proper knowledge of the overall gear speed and average it will produce to drive it. And this could be possible only if you give a read to the following article below.

Let’s start!

What Is Gear?

In the context of physics:

“A particular wheel that alters the various physical parameters (direction, torque, and speed) related to its rotational motion is known as gear”

Types of Gears:

Gears come in different shapes and sizes. But the overall shape remains circular because the gear calculations are totally dependent on its circumference. Anyhow, moving towards the gear types as mentioned under:

Input Gear:

A driven gear that transmits power to the output gear or source is called input gear. The input gear is always connected to a power source.

Output Gear:

The gear that is operated or rotated by the power provided by the input gear is called output gear.

Gear Train:

A special mechanical structure in which two or more gears work together in a meat is
known as the gear train. Look at the figure below:

gear train

In this figure, there are two gears working together to produce rotational torque. The input gear is connected to the motor while the output gear is connected to the shaft to carry out the function. You should keep in mind that both the gears rotate in opposite directions to smooth the process. And if you want to calculate the exact clockwise or anticlockwise rotation, you may use the rotation calculator.

One more important factor regarding motion of gears is that you must look for the motion direction. Now this direction may or may not be the same for different types of machine gears. Below we have given a pictorial view of rotational axes for different kinds of gears.

Gear axle ratios

Gear Ratio:

Simply put:

“The overall ratio of the input and the output gear based on their circumference is called gear ratio”

How To Calculate Gear Ratio?

The best way to determine the gear ratio is by utilising this online transmission gear ratio calculator. But we will also be taking you through the manual computational equations required to carry out the maths.

Gear Ratio Equations:

Let’s have a look at the relative formulas that you could use to calculate the gear ratio accurately.

Gear Ratio = (π * Diameter of Input Gear)/(π * Diameter of Output Gear)

The above expression relates the circumference of the input gear to that of the output gear. Moreover, we have also designed another swift circumference calculator that lets you calculate the circumference of the circle in a matter of seconds.

When only diameters or radii are taken into account:

Gear Ratio = (Diameter of Input Gear)/(Diameter of Output Gear)

Gear Ratio = (Radius of Input Gear)/(Radius of Output Gear)

The rear gear calculator also determines the results depending upon various input parameters.

When Input and Output Gear Teeth are taken into Account:

Gear Ratio = (Input Gear Teeth Number * (Gear Thickness + Teeth Spacing)) / (Output Gear Teeth Number * (Gear Thickness + Teeth Spacing))

For smooth running of the gear, the thickness of each tooth along with spacing must be the same. That is why we will vanish these parameters from the above equation:

Gear Ratio = Input Gear Teeth Number / Output Gear Teeth Number

Ways to Express Gear Ratio:

You can adopt various easy to express the mathematical form of the gear ratio. These may include:

Fraction Representation:

As fractions are also ratios, you can express the gear ratio as the fractional numerals.

Ratio Representation:

As the name signifies itself, the ratio is the comparison that is used to define the relative working of the gear’s teeth. You can better judge it by using this transmission gear ratio calculator.

Decimal Representation:

A decimal depiction of the gear ratio reveals how much revolution of the input gear you actually need to get full revolution of the output gear.

Understanding Gear Ratios:

In this section of the article, we will be taking you through the effect of the gear ratio on gear themselves.

Digging Deeper:

Let us suppose we have a gear train in which two gears are associated to mount and scroll over each other. The input gear is small, having 10 teeth. While on the other hand, the output gear is bigger, consisting of 40 teeth. To better determine their corresponding ratio, you may subject to this rear end gear ratio calculator rpm.

Gear ratios

Now if we talk about the gear ratio of both the gears, these are given as:

10/40 = 10:4 = 0.25

This illustrates that the four complete revolutions of the input gear will be sufficient to produce 1/4th of the output gear revolution. To relate these velocities better, we recommend you using the gear ratio calculator.

Idler Gears:

A particular gear that is inserted among input and output gears and changes the direction of revolution for the output gear is known as the idler gear.

Look at the figure below in which an idler gear has been installed in a gear train.

Now if the rotation of the output gear is clockwise, then this idler gear will change its rotation to counter clockwise and vice versa. Moreover, you may like to utilise our best rear gear calculator so as to calculate the actual gear ratio this idler gear would be producing among input and output gear.

Gear Ratio Chart:

Now the important factor to consider here is that the diameter of the tire is one of the most crucial factors that affect the gear ratio. If you are about to change your vehicles tyre of a considerable tire diameter, then you may get help from the following gear ratio chart:



25″ 2385 2568 2682 2804 2892 2988 3101 3259 3416 3590 3730 3984 4263 4482 4621 4700 4988 5390
26″ 2293 2470 2579 2696 2780 2873 2982 3133 3284 3452 3587 3830 4099 4309 4444 4519 4796 5183
27″ 2208 2378 2483 2597 2677 2766 2872 3017 3163 3325 3454 3689 3947 4150 4279 4352 4619 4991
28″ 2129 2293 2395 2504 2582 2668 2769 2909 3050 3206 3331 3557 3806 4001 4126 4196 4454 4813
29″ 2056 2214 2312 2417 2493 2576 2674 2809 2945 3095 3216 3434 3675 3863 3984 4052 4300 4647
30″ 1987 2140 2235 2337 2410 2490 2584 2715 2846 2992 3109 3320 3553 3735 3851 3917 4157 4492
31″ 1923 2071 2163 2261 2332 2409 2501 2628 2755 2896 3008 3213 3438 3614 3727 3790 4023 4347
32″ 1863 2007 2095 2191 2259 2334 2423 2546 2669 2805 2914 3112 3331 3501 3610 3672 3897 4211
33″ 1807 1946 2032 2124 2191 2263 2349 2469 2588 2720 2826 3018 3230 3395 3501 3561 3779 4083
34″ 1754 1889 1972 2062 2126 2197 2280 2396 2512 2640 2743 2929 3135 3295 3398 3456 3668 3963
35″ 1704 1835 1916 2003 2065 2134 2215 2328 2440 2565 2664 2845 3045 3201 3301 3357 3563 3850
36″ 1656 1784 1862 1947 2008 2075 2154 2263 2372 2493 2590 2766 2961 3112 3209 3264 3464 3743
37″ 1611 1735 1812 1895 1954 2019 2095 2202 2308 2426 2520 2692 2881 3028 3123 3176 3370 3642
38″ 1569 1690 1764 1845 1902 1966 2040 2144 2247 2362 2454 2621 2805 2948 3040 3092 3282 3546
39″ 1529 1646 1719 1798 1854 1915 1988 2089 2190 2302 2391 2554 2733 2873 2962 3013 3198 3455
40″ 1491 1605 1676 1753 1807 1867 1938 2037 2135 2244 2331 2490 2664 2801 2888 2937 3118 3369
41″ 1454 1566 1635 1710 1763 1822 1891 1987 2083 2189 2275 2492 2599 2733 2818 2866 3042 3287
42″ 1420 1529 1596 1669 1721 1778 1846 1940 2033 2137 2220 2371 2538 2668 2751 2798 2969 3208
43″ 1387 1493 1559 1630 1681 1737 1803 1894 1986 2087 2169 2316 2479 2606 2687 2733 2900 3134
44″ 1355 1459 1524 1593 1643 1698 1762 1851 1941 2040 2119 2263 2422 2545 2626 2670 2834 3063

The interesting fact to consider here is that our free gear ratio speed calculator also does calculations for your tyre gear average by taking the above transmission table values as a standard.

How Gear Ratio Calculator RPM Works?

In this section, we will guide how you could operate this calculator by entering the following inputs:


For Simple Mode:

  • Enter input and output gear teeth number
  • Likewise, enter the rotational speed and torque
  • At the end, hit the calculate button

For Advanced Mode:

  • From the drop-down list, select the transmission mode
  • Now enter the Engine RPM (Revolutions per minute), Axle Ratio, and Tire height in respective fields
  • Likewise, go for entering the Tire Width, Wheel Diameter, and Aspect Ratios in their designated fields
  • After you are done, hit the calculate button


The free gear ratio speed calculator does the following calculations:

  • Gear ratio (for 1-6 gears)
  • Mechanical advantage
  • Rotational speed and torque of gear axle
  • Width and height of the tire
  • Miles per Hour for a gear speed

Here you can also use our free angular velocity calculator to calculate the circular speed of a physical object moving.


What is a good gear ratio?

Normally, a gear ratio lower than 4.56 is considered better for smooth running of the gear, and thus the whole machine. If you want your ride to run without no knocking sound, then you should keep utilising this online gear ratio rpm calculator to keep an idea of your ride’s good performance.

Which gear ratio is faster?

Typically considered, a short gear ratio provides a greater speed. On the other hand, the shorter gear ratio provides you with the greater acceleration only in a specific direction.

Which gear ratio provides best fuel economy?

To drive heavier truck like vehicles, you must go for choosing a low gear ratio as 3.0, 3.23, or 3.31. But when it comes to the city cars, the axle ratio is not so affected by the MPG.

What gear ratio is better for torque?

3.73 is the optimal gear ratio that produces a heavier torque required to drag a heavy truck like vehicle. Usually, a greater axle ratio allows the axle to provide rear wheel (in case of a motorcycle) and front wheels (in case of a car) with more torque for smooth drive. Moreover, this online gear speed calculator will help you straightaway in determining the torque to move your car’s axle.

What is a 7.1 1 gear ratio good for?

In actual, the gear ratio 7.1:1 is used mostly for swim jigs in warmer weather, Froggin’, deep jigs, Flippin’, soft plastic stickbaits, topwater and late season jerkbaits.

What is a high gear ratio?

A higher gear ratio is one with a short numerical number. The lower your gear ratio, the higher would be the amount torque provided by it that you can keep calculating with a torque calculator for free.


Gear ratios are very important in estimating the overall performance of your ride’s gear axle. When you calculate the gear ratio with our best transmission gear ratio calculator, you actually get half of the information required to determine the overall speed range of your ride.


From the source of Wikipedia: Gear train, Mechanical advantage, Analysis using virtual work, Gear trains with two gears, Double reduction gear, Speed ratio, Idler gears, Belt drives

From the source of Khan Academy: Simple machines and how to use this tutorial, Lever, Wheel, pulleys

From the source of Lumen Learning: Simple Machines, Forces and Torques