Summarize the following:
Go through your clothes and pick out a garment with sleeves that are form-fitting yet comfy. This is usually a good sign that the arm holes are just the right size for you. It doesn't matter how long the sleeves arethe shirt you choose could be a t-shirt, sweatshirt, blouse, dress shirt, or sweater. It could even be sleeveless, as long as it has stitched arm holes. This method can come in handy when you want to get a better idea of your ideal arm hole size but don't feel confident in your ability to measure your own arm yourself and don't have anyone around to help you. All you have to do now is use basic math to find the sum of the pair of numbers you just wrote down. If the front seam was 714cm (2.9in) and the back seam was 712in (19cm), your final arm hole measurement would be 1434in (37cm). Add up your fractions carefully. If you make a mistake, your new shirt may not have the perfect fitted look that you were going for. Keep in mind that the number you end up with will only be an estimate of your true arm hole measurement, and won't be as accurate as more traditional measuring methods. Even so, it should still help you achieve a satisfactory fit when ordering or making tailored clothing.
Find a shirt or top that fits you well. Add the two measurements together to get your full arm hole measurement.