I have found specifications listed by vendors to be highly unreliable and have decided that the only way to get reliable measurements is to do them myself. It's easy to measure straight blades because the distance between the base and the tip is the same as the total blade length. But it's not so simple with curved blades. Anyone know of a system/formula to get an accurate measurement?

Here's how to do it on a Japanese sword. http://www.japaneseswordindex.com/measure.htm

The same method applies to other curved swords, but the terms will be different.

Curved blades are generally measured from the guard to the point in a straight line.

Cheers

GC

Only if you think it is misleading to describe a persons height not taking into account the curvature of their spine.
If you were talking about the length of the cutting edge, then yes, you would measure differently (and from memory that is a measurement taken for nihonto) but that would be different from the blade length for straight bladed swords as well (and flammmards would be a nightmare to discuss).