Gear Ratio Calculator

Gears are one of the most important mechanical elements that are used in nearly all types of machinery. Proper design and calculations of gears are very important, and this needs an engineering-level approach. So, the gear ratio calculator is very important in this way.

When you are designing your gear systems for machinery, you need to know the required gear ratio to obtain the required torque and speed. This article will be a very good reference to calculate your required gear ratio for input and output torques and speeds, for gear pairs.

The gear ratio is a very important factor in the design of gear systems. You need to define it correctly. Because the speed and the torque of a system directly depend on this gear ratio value. So, you need to use the gear ratio calculator to calculate these factors effectively.

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How to Use Gear Ratio Calculator?

Gear Ratio Calculator for Gear Systems

As you see above, you need to enter the required values to obtain output torque and speed from a gear system.

Gear systems are used for generally torque speed reduction. There is a main shaft that gives input speed and torque to the gear system. This output shaft is assembled to a gear which is called ‘driving gear’. Other gear which is assembled to other shafts, is called ‘driven gear’.

In here;

n1: This is the number of teeth in the input gear. There is no unit.

n2: n2 is the number of teeth of the output gear. Also, this value has no unit.

Input Speed: The rotational speed of the input shaft and gear. The unit is RPM.

Input Torque: This is the torque value of the input gear. The unit of the torque is N.m or lbf.ft

Output Speed: Output speed is the total speed of the output shaft and gear. The unit of the output speed is RPM.

Output Torque: This is the output torque of the output shaft and gear. Unit is N.m or lbf.ft in English units.

Click on the ‘Calculate!’ button to see the output torque and output speed of the second shaft and driven gear.

If you want to do another calculation, click on the ‘Reset’ button and enter new values.

Gears in Machinery

Gear ratio is very important in machinery.
Image Source:

Gears are very important in machinery. Maybe they are the most important part of most of the machines. We are using gears generally for power transmission at specific rates. Because of it, the gear ratio is a very important value to calculate. You can use this gear ratio calculator for it.

According to the gear ratio, we make conversions between the torque and rotational speed. Because with the increasing rotational speed and torque the transmitted power increases. But in general, the generated power is constant in general machinery.

For example, an internal combustion engine produces a specific power. And with a transmission system, this power is transmitted in a specific torque and RPM to wheels. So, with the increased torque, the RPM decreases. Also with the increasing RPM, the torque decreases. And also for internal combustion engines, you can use a gear ratio calculator.

For different situations, we need different torque values. So, you can adjust the torque and speed values with the gear systems in transmission.

Importance of Gear Ratio

With this example, you will understand the gear ratio.

We can calculate the torque, power, and RPM relation with this equation;

Torque * Speed / 9.55 = Power

In this equation, the unit of the torque is N.m. And the unit of speed is RPM. The unit of power in kW.

So, for constant power; we can increase the torque by increasing the number of teeth of the second gear. But also, the speed of the gear decreases. Also if we decrease the number of teeth of the second gear, the speed increases. But torque decreases.

We can adjust the torque and speed between the gears by adjusting the gear ratio. A gear ratio calculator is best for it.

Applications of Gear Ratio Calculator

There are lots of kinds of applications of gear ratio in engineering.

Transmissions in Automobiles

Automotive transmission.
Automotive transmission(Image Source:

This is one of the most important applications of gear ratio in engineering. You know that a transmission has 5 gears and 6 gears. With the increasing gears, the speed of the car increases. Also with the decreasing gear, the speed decreases but traction increases.

So, with the increasing gear, the gear ratio decreases. With the decreasing gear ratio, the total torque decreases but speed increases. The power of the engine is constant.

Also with the decreasing gear, the gear ratio increases. So with the decreasing gear ratio, the total torque increases, and the speed decreases.

In the design of transmission systems of automobiles, you can use the gear ratio calculator. You can calculate each of the gear pairs to obtain specific torque and speed values. for each gear.

Reducer Gears

We use reducer gear systems in different engineering systems to reduce the RPM of an electrical engine to a specific value. So, there are gear systems and a bunch of gear pairs in reducers. These gear pairs have specific gear ratio values to reduce the RPM. But also, the torque increases.

For example in low-speed mixers, electrical engines are used to produce the required power. But, the shaft of the electrical engine rotates at very high speeds. So, a reducer gear set is used to decrease the rotational speed but increase the torque. Because we need torque to mix the high viscosity mixtures.

Also, you can use the gear ratio calculator in the design of reducer gears. In reducers, generally, there are several gear pairs. You can calculate the gear pairs to obtain a good system.

Clockwork Mechanisms

Gear systems have also a very important place in the clockwork mechanisms. The source of power in the clockwork mechanisms is a strained spiral spring. This spiral spring produces the power to rotate the gears in a clock. These gear pairs are designed to obtain the required movements of an hour and minute hands.

So, in the design of clockwork mechanisms, you can use the gear ratio calculator to calculate the specific speeds and torques between the gear pairs.

Gear Mechanisms of Bicycles

If you take a look at the gear mechanisms of bicycles, you will see a set of gears at the front and the rear side. There is a chain system between these gears. You are adjusting the gear ratio with this chain. With the increasing gears, the gear ratio decreases, so speed increases. Also, if you need more traction, you adjust the gear to lower values.

So, you can use the gear ratio calculator in the calculation of gear ratios of bicycle gear systems.


So, a gear ratio calculator is a very important tool in the calculations of torque and speed of different systems. Furthermore, you can save lots of time in the calculation of different gear systems. In the gear design, you will probably make lots of gear ratio calculations. This calculator will be a very big companion for you.

Also, you can use the gear ratio calculator in the design of gear reducer systems, automotive transmission systems, bike gear systems, and other kinds of gear pair systems.

Finally, Mechanicalland does not accept any responsibility for calculations done inside its calculators. As a good engineer, check your calculations by hand.

Above all, units are very important. Units are not important for this calculator. You will see the ratio of what you entered. But if you need to convert your units into another set of units.

Take a look at the other engineering calculators that are available in Mechanicalland!

So, do not forget to leave your comments and questions about the gear reduction calculator below.

Your precious feedbacks are very important to us.

FAQs About Gear Ratio

Why does gear ratio affect speed?

Because there is a strict relation between the torque and speed. With the increasing gear ratio, speed increases. Because the diameter of the second gear decreases. So, the output gear will rotate faster. But, torque decreases. You can use the gear ratio calculator to make speed calculations.

Does gear ratio affect horsepower?

There is no relation between the horsepower of a system with the gear ratio. The power is always constant in gear systems. The gear ratio affects only torque and speed. Torque, speed, and power are related terms. You can see the torque and speed relations with the gear ratio calculator above.

Does gear ratio affect the gas mileage?

With the top gears, the car will move faster. But in low gears, the speed will be low. The engine produces the same power and consumes the same fuel. So, with the increasing gears, you can take more distances with the same power. This means the gear ratio affects the gas mileage. You can make the required calculations with the gear ratio calculator above.

How gear ratio is calculated?

The gear ratio is the ratio between the input gear teeth and output gear teeth. We calculate the gear ratio with input and output teeth numbers of gears.

Why gear ratio is important?

Because it affects the torque and speed of a system directly. Torque and speed balance is very important in lots of mechanical systems. You can make calculations with a gear ratio calculator to see the importance of it.

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One response to “Gear Ratio Calculator”

  1. Jim Todd Avatar
    Jim Todd

    Gear reduction calc interesting but as a backyard maker using trial and error more than thoughtful foresight as my natural process it seemed too complicated for me to use. I probably didn’t devote enough effort to understanding it!

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