online burn calculator accuracy

ahoy_m8 Posts: 3,053 Member
Online calculators are notoriously inaccurate, or so I read. Two questions about that:

1) Is the inaccuracy a function of body comp? I.e., are they more/less accurate for someone with more/less BF%?

2) For people who have HR activity trackers, what is the magnitude of the discrepancy (online calculator vs. HR tracker) for you? (I'd be especially interested in women runners/walkers with 18-20%BF.)

All insight, opinions & speculation appreciated.