Measuring Guide
It's best to be measured wearing the exact undergarments, slip, and shoes you will be wearing on the day of the wedding or event. If you don't have them yet, wear the closest approximation: most importantly, heels of the same height. Don't forget pantyhose or Spanx if you plan on wearing these. Also, wear the same bra or corset you plan on wearing.

For all measurements keep your thumb behind the tape and do not pull it tight. Remember: in all cases you want to round up! It is easier to take your dress in than it is to let it out.
Not your bra size! Measure around your back across the fullest part of the bust. Arms should be down and relaxed at your sides. You should wear a bra when taking this measurement.
Also known as natural waistline. Measure around the smallest part of your waist. This is typically an inch or two above your belly button.
Stand straight with your heels together and arms down at your side. Measure across the widest part of your hips, across the hipbone.
Hollow to Hem
Starting at the hollow found at the base of your neck (front), measure straight down to where you want the hem of your dress to end. You should stand upright and your feet should keep together. It is recommended that you wear the same shoes you plan on wearing on your wedding day to guarantee that the dress will actually end where you want it to end.
Shoulder to Waist
Measure from the top of your shoulder, go down over the top of your nipple to your natural waistline.