In order to integrate loadouts in the website the total weight of the loadout would be a great thing to have.
Observations:
In the config editor there is a weight attribute, but appears to be zero for all equipment and weapons.
There is a mass attribute, but in its current form it is nonesensical
This might be simply impossible to do automatically.
BI does not comment on how they calculate it.
And my own analysis on a limited set shows that the ratio mass/kgs is somwhere in between 18 and 22.
So it is clearly not a constant value.
Looking up 170 values in game is not going to be fun, but probably the only way to go about it.
Unless, .... I manage to figure out how ACE does it in their arsenal....
The actual formula:
format ["%1kg (%2lb)",((_mass * 0.1 * (1/2.2046) * 100) / 100) ToFixed 2, ((_mass * 0.1 * 100) / 100) ToFixed 2]