The most important measurement is your chest measurement.
Measure around your entire chest just below your armpits. For those of us whose stomach goes farther out then our chest, use the larger measurement. Compare that measurement to our actual jacket chest measurement on the chart above. Most people like to order a jacket that measures about 2 inches larger then their actual chest measurement to accommodate for a sweater or under shirt.
Sleeve Length is measured from the bottom of the collar, where it meets the shoulder, down the sleeve to the end of the cuff.
Jacket Front Length is measured from the collar seam down to the bottom of the longest part of the front.
Jacket Back Length is measured from the collar from the collar seam to the longest part of the jacket back.