Calculations behind our poster "occupancy by discipline" can be explored with the calculator below. The default values in the calculator below will result in an "occupancy" of 85,500, as per the poster. This is a value that you may wish to challenge, and we encourage you to do this!

For example, you might:

1. Add an allowance for "non-human items" (a typical value for desks, chairs, paperwork, and plants might be 0.50kN/m2 - approximately 50kg/m2, which is the same as two bags of cement per square metre, or 20 reams (10,000 sheets) of A4 paper per square metre).
2. Add an allowance for partitions (normally added on top of the imposed floor loading, for example you might have a total Imposed Floor Load = 3.5kN/m2, made up of 2.5kN/m2 + 1.0kN/m2 for partitions)
3. Change the utilisation factor from 1.00 (assumed here, see note 3) to 0.80 (commonly assumed by designers).
4. Change the weight of your humans (0.75kN average is assumed here)

Note 1: In the calculations we assume 95% of the floor area is loaded to the value your provide. In the UK it is standard practice to apply a higher floor load of around 7.5kN/m2 over the remaining 5% of floor area. We do not consider this in the calculation of occupancy.

Note 2: The "Total Imposed Floor Load value" entered here should include any allowance for partitions and non-human items. So, if you have a floor load specification of 2.5kN/m2 + 1.0kN/m2 you would enter 3.5kN/m2 in the "Total" row. Below that, you enter 1.0 as the partition load. And below that you choose some value of the 2.5kN/m2 that you want to allocate to "non-human items".

Note 3: BS EN 1991-1-1 allows for columns and walls that the total imposed loads from several storeys may be multiplied by a reduction factor. This is calculated in different ways in different countries, but gives a number normally between 0.50 and 1.00. In the calculation below, you could imagine you are designing the ground floor column. As an example for the UK, a 30,000m2 structure with 16 storeys would give a reduction factor of 0.50 for the ground floor column.

Note 4: The Utilisation Factor is the value chosen by the designer as a ratio between actual performance value and the maximum allowable performance value which is deemed limiting for a structural member. For Eurocodes, this is the ratio between "Ed" and "Rd". In the UK it is normally taken by designers as 0.80. In the poster, we have assumed a Utilisation of 1.00 (i.e. Ed = Rd). A utilisation factor of 1.00 is safe - see BS EN 1990, e.g. Equation 6.8 for equilibrium at the ULS, or Equation 6.13 for SLS.