If you are serious about your leaders and tippets you need a gauge to measure the tippet size. Especially if you are tying your own leaders. I use the Mike Rite and it is very well made. I have used mine for years. It is one of those tools every vest should have. I have used a Machinist Micrometer but you have to be much more careful to get an accurate reading.
When you use a Mike Rite you lay the tippet or mono over the slot in the tool, the one it lays into is the correct size of the material. You want a tight fit but not so tight that you have to force the mono into the tool. This way you will always know where the tippet ends and the front taper of the leader begins.
Another thing you can do is determine the tippet/leader transition point and tie a loop on the tippet. Now you can loop your tippet on and the leader will last much longer. Here is how I do it.
1. I take a new tapered leader and determine the tippet/leader transition point using the Mike Rite.
2. I cut off all but about 6" of the tippet. So I now have a leader with a 6" tippet measured from the tippet/leader transition point.
3. I tie a Perfection Loop or Non-Slip Mono Loop in the end of the 6" tippet.
4. I take 20 inches of tippet material and tie a Perfection Loop or Non-Slip Mono Loop in one end.
5. I Loop the tippet to the leader and you are ready to fish. You can now tell when the tippet is getting short and if it is time to replace the tippet.
Mike Rite Tippet Gauge
Fishpond Firehole Tippet Gauge