Ombrelieveable!

As you may have gleaned from a previous post, I've got a zazzy ombre handpainted shawl on the needles...

 

 and I forgot to weigh the yarn before I started, which in my world means there is no way for me to tell how much yarn is getting used.  My evolution as a knitter has led me in a very spreadsheet-and-scale-based direction; for someone who doesn't like math very much, I tend to depend on it in my crafting, even when faced with harsh non-theoretical realities (I'm looking at you, swatches, you lying liar liefaces).

Generally I have a spreadsheet, and in that spreadsheet I precisely estimate the total stitch count for the project and set it up to automatically calculate completion percentages; I can then weigh the remaining yarn as I go to evaluate and figure out oh, I have used 50% of my yarn to complete 75% of the estimated total, I can make the shawl bigger than originally planned.

But without that system?
Flying blind!  Who even knows?  Magic!  Unicorns are real!

The yarn arrived already caked up and pretty:

More art than science!

so in the face of my poor planning, I absolutely stabbed a guess that each color segment was roughly a third of the yarn...

Turns out: not true.  I ran out earlier than budgeted and skipped straight from 86% done to OOPS BINDING OFF NOW:

Thank goodness I found Jennifer Dassau's tricks for predicting how much yarn one will need for a bindoff row.  Two inches left at the end.

Anybody have a middle ground for estimating yardage, some reckoning midway between vanilla computation and a reckless shot in the dark?