To check the waist size on crop you already have please lie them flat, don't bring the front of the waist up to match the back of the waist

Lie them flat & measure across the very top inside the waistband that is & double the measurement to get your waist measurement

Please keep in mind different styles of crop sit differently & the rise makes a difference too

To check your inside leg length please lie crop trousers flat & measure from the crotch to the hem