Actually, I've weighed a bunch of fly lines lately. For what it is worth...

The tip section length is often given on the box or company website. Usually it is 6" for a WF and 12" for a DT. I've found the tip sections weigh 2-6 grains.

I use a little digital scale that measures directly in grains. Because little digitals can struggle with very light weights, I weigh the tip section by difference. I place something on the scale and note the weight. I plunk the tip section on top, note the weight, and do the math. For the line weight I measure off 30' of line (plus tip), weigh the line, and subtract the tip weight.

Most fly lines were very close to their marked AFTMA size. Every DT line I checked was within specification. But one new WF line, from a box clearly marked "weighted heavier", was well into the tolerance for the next line size.

If all this sounds like too much effort, you're right. Don't bother with the science. Just read the box and use 'em.


Tom