where
T = Torque Nm
F = Bolt Load N
p = thread pitch mm
u = coeff friction (0.1 to 0.2 typically)
Rm = mean thread radius mm
r = mean nut bearing radius mm
u will vary considerably depending on type of lubricant, finish and fit of threads.
Looks roughly the same as the other formulas. I'd use the formula T=kdf where T is torque, k is a friction factor (commonly 0.18 for well lubed nuts and studs), and f is force you will have 61 kN or 14 kips on your bolt. Well within the allowable for most steels under ordinary temperatures.
Well, since (depending on your definition) a ton is either 2 kips (2000 lb) or 1000 kg (roughly 10 kN) then your result of 5.6 tons is roughly 56 kN or 11 kips. Pretty close to the values I came up with above. I'd guess your on line calculator used a slightly different friction coefficient, but the results are certainly reasonable.
Keep in mind that translating torque on nuts to force on a bolt is a very rough calculation. There are too many details involved (friction/lube, tolerances, temperature, phase of the moon) to pretend that the correlation is extremely accurate. Close enough usually is. If not, use stud tensioners, direct tension indicators, etc.
