# Using `clamp` to handle font sizing

Mike Foskett has created a very simple and helpful calculator for generating clamp values with several different options. You can find the Fluid-responsive property calculator here.

The `clamp` function in CSS allows us to set a minimum value, maximum value, and a value that the `font-size` should be when the value is in between the minimum and maximum. In our example for the heading, we're setting a `36px` minimum, a `56px` maximum, and a calculated value `calc(2.25rem + ((1vw - 3.6px) * 1.2821))` as our "middle" value.

The "middle" value in our clamp function is the value that will apply when the calculation renders a value that is between our defined minimum and maximum. Otherwise, if the calculation is too low the function defaults to the minimum value and if the calculation is too high the function will default to the maximum.

The MDN article on `clamp` is a great resource to learn more. If you do not need to support IE, `clamp` has excellent browser support .

If you wanted to, you could also use the calculator to handle your `clamp` values in `rem` or even `em` in order to maintain a typescale. It's easiest to demonstrate clamp using pixel values though.

Note: The `calc` base value ( `2.25rem` ) MUST be stated in `rem` to maintain accessibility. Where: `1.2821 = 100 * font-size_difference / viewport_width_difference`