A worked example: 50 m² residential floor
A 50 m² floor with a dead load of 1.5 kPa and a live load of 2 kPa has a total design load of 3.5 kPa (1.5 + 2), which represents a total force of 175 kN spread across the floor (3.5 kPa × 50 m²).
The addition: total load = dead load + live load
Dead load is the structure's own permanent weight — slab, finishes, fixed partitions — and stays constant for the life of the building. Live load is the variable load from occupancy and use — people, furniture, stored goods — and is specified per the applicable building code (IS 875 Part 2 in India) based on how the space is used. Adding them gives the total design load per square metre the floor must be built to carry.
Why occupancy type changes the live load figure
A heavier-duty floor makes the difference concrete: an 80 m² office floor with a heavier 2 kPa dead load (a thicker slab) and a 3 kPa live load (IS 875's typical office occupancy figure, higher than residential) totals 5 kPa — a total force of 400 kN across the floor. The same arithmetic, but a different occupancy pushes both inputs — and therefore the total — noticeably higher than a residential floor of the same size.
From load per square metre to total force
The per-square-metre figure (kPa) is what building codes specify and what a structural engineer designs against directly. The total force (kN) — the load figure multiplied by the floor area — is useful for sizing the beams and columns that ultimately carry that floor's full load down to the foundation.
What this calculator does not do
This is deliberately just an addition and unit-conversion step — it does not apply the load factors or load combinations (such as 1.5×dead + 1.5×live for ultimate limit state) that a building code requires for an actual structural design. Those factors, and the dead/live load values themselves, must come from a licensed structural engineer working to the applicable code.