We just received the Winter + Spring MAP 2-5 scores for our 2nd grader. The school's printout includes only the raw scores and lacks percentiles based on 2015 data. So, I researched the topic a bit and created an interactive calculator to convert scores to their 2015 national percentiles:

NWEA Score Percentile Calculator

It has built-in the 2015 tables for Begin, Mid, and End-Year for Math, Reading, and Language Usage as published here.
The conversion uses a standard z-Score computation via math.js's erf. Google analytics is enabled on the site.

The usual caveats apply (in Math, there's not one, but 3 tests (K-2, 2-5, and 6+), so scores shouldn't be compared except when the same test was taken), and of course this is an achievement test, not an IQ test, and there's apparently no research on how well gifted children do on the MAP test.

Still, I hope this may be useful to others, particularly if their school reports do not include percentiles, which is why I'm sharing it here. NWEA publishes the same data but in table form and without the interactive calculator/coloring part.