Ratio Calculator allows you to compare the ratios and find one missing value from three known numbers.
Ratio Calculator is a free online tool where you can compare two ratios and find one missing value. The main operation of the calculator is to solve the ratios using the three values provided by the user and find one missing value. Also, it helps you to find the aspect ratio of two sizes or objects.
The ratio can be simply defined as the mathematical relationship between two numbers that are used to express the proportion of the first number containing the second number.
We can write the ratios in following terms:
15:7 or 15 to 7 or 15/7
Let's understand it using an example. In a school, it is said that for every 50 students there is 1 teacher. Therefore, the ratio will be 50:1 between students and teachers. So, if the number of students is 150 so there would be 3 teachers.
Ratios are also used to show the interrelation between two sizes. There can be more complex ratios depending upon the use cases. For example, for every 50 students, there is 1 teacher and 2 staff members, so the ratio will come out as 50:1:2.
The ratio is dimensionless. So, it doesn't have any units. Also, it is widely used to compare the width and height of any object. Like screen sizes and video resolutions. In addition, it is used in business metrics, science, decisionmaking strategies, accountancy, statistics, etc.
It's obvious that our Ratio Calculator is the best tool that will help you to calculate the missing part to make both the ratios equivalent. So, let's understand the mathematics used under the hood of the calculator. It's time to know how does the calculator works?
The proportion equation we have:
A : B = C : D
or, A / B = C / D (in fraction)
or, A × D = C × B (by cross multiplication)
Now, we can easily manipulate the above equation to solve for the one value we need.
If we need to find the value of D and we have A, B, and C, then the equation will be:
D = 

Similarly, the equations for the other values are:
A = 

B = 

C = 

The stepbystep process to solve for an unknown value will be as follows:
Let's work on an example problem to make it even more clear.
12 : 18 = C : 5
Find the missing value C.
12 : 18 = C : 5
Firstly, let's convert the ratios into fractions.

= 

C = 

= 

= 

So, C = 3.333
Hence, the missing value in the equation was 3.333 to make both the ratios equivalent.
Our calculator is very simple to use. But there are some important rules you need to keep in mind.
Necessary Rules:
Now follow the steps below to use the Ratio Calculator:
Ratio is used for comparing two quantities or sizes. Whereas proportion is the equality of two ratios.
It's widely used to compare two values or sizes.
Let's suppose you have an image of 1920 width and 1080 height. Now you want to resize it and make the image width 1000 without losing image resolution. In this situation, you can compare the two ratios and find the height of the image using our calculator. When you input the three sizes into the calculator, you will get 562.5 height. So, if you want to resize your image for 1000 then you should keep the height as 562.5. It will make your image ratio equivalent to the original image.
Our calculator only accepts integer and decimal numbers. You can't enter negative or fraction values.
There is no defined limit on the input size. So, you can write any digit value inside the input box.