Lets try again.
The radiator in your picture is small,
it is in a small room, so it probably
gives out less 1 Kwh..
So lets ignore its output as its
irrelevant.
Lets look at the size of your boiler, if
you intend to fit underfloor heating,
then the first issue is, the size of the
boiler, its output, in Btu or Kwh.
Does it keep your home comfortable
at present?
Is it flat out in cold weather, or at say
three quarters output?
If you have the spare heating
capacity OK?

Now, let look at the room you intend
to heat with underfloor heating.
What type of floor do you have at the
moment?

How do you intend to fit the
underfloor heating?

The recommended standard, is to lay
four inches of styrofoam insulation
on the floor. Cover that with a
waterproof membrane.
Then starting in the middle of the
room lay a spiral of pex pipe over the
styrofoam, fixing it in place with
plastic staples, then poor three or
four inches of concrete over and
level.

Or lay four inches of styrofoam on the
floor, then lay strips of wood in
parallel lines on the styrofoam, laying
the pex between the wood strips and
cover with three quarter thick ply.

Either way the floor level goes up,
requiring alteration to things like
-doors, baseboards etc; adding a lot
of work.

If you don't use four inches of more of
styrofoam or similar, then a lot of
your heat input will be wasted as
heat always goes to cold.