If this is the first time for you to order contact lenses, you can find the prescription of your eyes as below

They are significantly different because eyeglass lenses are positioned approximately 12 millimeters from your eyes, whereas contact lenses rest directly on the surface of your eyes.
If you want to wear both contact lenses and eyeglasses, you will need two separate prescriptions.
You can simply find your contact lenses prescription as below:
Please note that the table below only provides the details of a myopia(nearsightedness), which is with -SPH prescription.

Eyeglass
Contact lens
Eyeglass
Contact lens
below -4.00
same as eyeglass
-7.75
-7.00
-4.00
-3.75
-8.00
-7.25
-4.25
-4.00
-8.25
-7.50
-4.50
-4.25
-8.50
-7.75
-4.75
-4.50
-8.75
-7.75
-5.00
-4.75
-9.00
-8.00
-5.25
-5.00
-9.25
-8.25
-5.50
-5.00
-9.50
-8.50
-5.75
-5.25
-9.75
-8.75
-6.00
-5.50
-10.00
-8.75
-6.25
-5.75
-10.25
-9.00
-6.50
-6.00
-10.50
-9.25
-6.75
-6.25
-10.75
-9.50
-7.00
-6.50
-11.00
-9.75
-7.25
-6.50
-11.25
-9.75
-7.50
-6.75
-11.50
-10.00