If you do want to change the FOV instead of the sens, you should bear in mind you are nearly always more limited by FOV options in games, especially if you like the upper end of them.
But with a calculation you can work out the new FOV needed to match focal length on the new screen size instead of changing sens...
You can do newFOV = 2 * (arctan( screenSizesRatio * tan( ( oldFOV * π / 180) / 2))) * 180 / π
so if the oldFOV was 90 degrees on the 24 inch, and the screenSizesRatio is 27/24 = 1.125.....
we then have: newFOV = 2 * (arctan( 1.125 * tan( 1.5708 / 2 ))) * 180 / π
so newFOV = 96.73 degrees on 27 inch