Employment density: turning floorspace into job numbers
Every job figure in a planning application comes from a density assumption. Get the area basis and the use category right, or the whole economic case is overstated.
Employment density is the number that converts floorspace into jobs. It is expressed as square metres of floorspace per full-time equivalent job, and it sits underneath every claim in a planning application about how many people a scheme will employ. Get the density wrong, or apply it to the wrong measure of area, and the economic case reads as unreliable before an officer has considered anything else.
For a developer promoting employment land, this matters more than it used to. Job numbers now feed the planning balance, section 106 employment and skills obligations, health impact work and, on larger schemes, the case that the benefits outweigh a policy conflict.
The arithmetic, and the area basis
The calculation is simple. Take the floorspace, divide by the density figure, and you have a full-time equivalent job estimate. A building of 6,000 square metres at 12 square metres per job produces 500 jobs. At 70 square metres per job, the same building produces about 86.
The trap is the area. Densities are published against a defined basis, and the two in use are net internal area, which excludes circulation, plant, cores and structure, and gross internal area, which includes them. Office densities are normally quoted against net internal area. Industrial and warehouse figures are normally quoted against gross internal area.
Apply an office density to a gross figure and the job estimate inflates by the whole efficiency allowance, which on a multi-storey building with a central core is not a rounding error. Every appraisal should state the area basis in the same sentence as the density, and every table should label its columns accordingly.
Where the figures come from
The standard English reference is the employment density guide published by Homes England, which sets out figures by use category together with the area basis for each. It is public, it is widely used by local authorities in their own evidence base, and using it means arguing about application rather than about source.
Broad patterns from that work are worth holding in mind even before you look up a specific figure. General office space sits at the dense end, in the region of 12 square metres per job on a net internal basis. General industrial is much less dense, in the order of three times that on a gross basis. Warehousing and distribution is less dense again, often around double the industrial figure, and large scale automated distribution can be far below even that. Check the current edition for the figure that applies to your use class rather than working from these ranges.
Some authorities publish their own assumptions in an employment land review or an economic development evidence base. Where the local figure and the national guide differ, use the local one and say so, then show the national figure as a sensitivity. An employment land assessment is the natural place for that comparison, because it is already dealing with supply, demand and the quality of existing stock.
The uses where the standard figures break down
Data centres are the clearest example. They occupy large floorplates and employ very few people, since the job count is driven by operations and security staffing rather than by area. Applying a general industrial density to a data centre produces a job figure several times the truth, and objectors will say so.
Automated distribution is the same problem in a different sector. Two warehouses of identical size can differ by a factor of several in headcount depending on the degree of automation, and the density guide's average sits somewhere between them. Where the occupier is known, use the occupier's own staffing schedule and say that is what you have done.
Flexible Class E space causes a third difficulty, because the same unit can be an office, a shop, a clinic or a gym without a further application. On a speculative building the honest approach is a range, presented with the assumptions behind each end of it, rather than a single number based on the densest plausible use.
Mixed use schemes need the calculation done floor by floor, not by applying a blended figure to a total. That is more work and it is the version that survives scrutiny.
From gross jobs to net additional jobs
A gross job figure counts posts on the site. It says nothing about whether those posts are new to the economy. Appraisal practice, following the Treasury's approach to additionality, asks four questions.
Deadweight: would some of this activity have happened anyway, elsewhere in the same area? Displacement: does the scheme take trade or labour from existing businesses nearby? Leakage: how many of the jobs go to people living outside the area the benefit is claimed for? Multiplier: what indirect and induced employment follows in the supply chain and through spending?
Working through those produces a net additional figure at a stated geography, which is what a decision maker can weigh. The gross number is still worth reporting, clearly labelled, because it describes the site itself. An economic impact assessment should carry both, with the assumptions visible.
Be careful about geography. Net additional jobs "in the district" and "in the functional economic market area" are different numbers, and the second is usually larger because displacement within the district disappears at the wider scale.
Where density evidence gets used
| Context | What the figure is doing |
|---|---|
| Economic impact assessment | Estimating operational jobs for the planning balance |
| Employment land review | Converting job forecasts into a floorspace requirement |
| Loss of employment land | Testing what employment is being given up |
| Section 106 employment and skills plans | Setting targets for local recruitment and apprenticeships |
| Health impact assessment | Describing employment effects on the local population |
The second row runs the calculation backwards, from forecast job growth to the hectares of land a plan needs to allocate. That is where density assumptions shape development plans rather than individual applications, which is worth understanding alongside what counts as the development plan and how windfall allowances are justified in the same evidence base.
Section 106 employment obligations deserve a note of their own. A target expressed as a percentage of jobs is only as good as the job estimate it is calculated from, so an inflated density produces an obligation the occupier cannot meet. Negotiating those targets against an honest figure protects the scheme later.
An illustrative calculation
Illustrative example. A speculative unit of 9,000 square metres gross internal area, proposed as flexible industrial and storage. At a general industrial density the estimate lands in the low hundreds of jobs. At a large scale distribution density it lands closer to one hundred. The application presents both, states the area basis, explains that the end user is unknown, and applies a displacement assumption drawn from the council's own employment land review. All figures are illustrative.
State your density, your area basis and your source in one place in the report. Reviewers check that first, and an appraisal that hides the assumption invites the least generous reading of it.
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Frequently asked questions
What is employment density?
The amount of floorspace associated with one full-time equivalent job in a given use, expressed as square metres per job. Multiply floorspace by the reciprocal and you get an estimated job number. It is an averaging tool for appraisal, not a measurement of any particular occupier, and it should always be presented as an estimate.
Which published figures should I use?
The Homes England employment density guide is the standard English reference and gives figures by use category, along with the area basis each one is measured on. Local authorities sometimes publish their own assumptions in an employment land review. Where the two differ, state which you have used and why, rather than picking whichever gives the better number.
Does the area basis really matter?
Yes, and it is the most common error. Office densities are usually quoted against net internal area, while industrial and warehouse figures are quoted against gross internal area. Applying an office density to a gross figure inflates the job estimate by the whole efficiency allowance, which on a multi-storey building is substantial.
How should construction jobs be reported?
Separately, and in person-years rather than as permanent jobs. A build programme generating a given number of person-years of work is a real economic effect, and it is a different thing from an operational job that persists after handover. Combining the two into one headline figure is the quickest way to lose an inspector's confidence.
What about displacement and additionality?
A job that moves from one town to another is not a new job in the wider economy. Appraisal guidance asks for deadweight, displacement, leakage and multiplier effects to be considered, so a gross job figure should be followed by a net additional figure at the relevant geography. Authorities increasingly ask for that second number.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.