Prefab Module Count Calculator
How many volumetric modules a building needs, how many truck loads that is, and how many days of craneage — the logistics that decide whether modular construction works for a project.
A volumetric module is limited by what a truck can carry: about 4.
How the prefab module count calculator works
A volumetric module is limited by what a truck can carry: about 4.2 meters wide and 14 long on most roads without escort. Divide the floor area by the module area, allowing for the module efficiency, and you have the count.
Each module is one truck load and, on a good day, one crane lift in 20 to 30 minutes. That is why modular buildings go up in days — and why site access and crane time are the constraints, not the factory.
Formula: modules = floor area / (module area × efficiency); site days = modules / lifts per day
Worked examples
| Inputs | Modules required | Note |
|---|---|---|
| 3,200 m² in 12 by 4.2 m modules | 73 | about 73 modules, five days |
| Smaller modules | 127 | more loads, more days |
| An oversize module | 61 | needs an escort |
FAQFrequently asked questions
How big is a volumetric module?
Whatever a truck can carry — up to about 4.2 m wide and 14 m long without an escort on most roads. Wider modules exist but cost more to move.
What is module efficiency?
The share of a module's footprint that is usable floor after double walls at the joints and the structure. Eighty-five to ninety per cent is typical.
How fast does a modular building go up?
Ten to twenty modules a day with a good crane and access — so a mid-size building is enclosed in a week. Fit-out and connections take longer.
What limits modular construction?
Site access for the trucks, crane reach, and the design being repetitive enough to suit modules. A bespoke plan loses most of the benefit.
Is it cheaper?
Faster, more predictable, and usually similar in cost. The saving is in programme and finance, not the modules themselves.
Where these figures come from
- Sabine (1922) — Collected Papers on Acoustics — the reverberation-time equation
- CIBSE Guide A — Environmental design — daylight, comfort and ventilation criteria
- Neufert — Architects' Data — the standard reference for space and dimension
- International Code Council — International Building Code — occupant load and egress factors
- International Code Council — publisher of the model codes most US jurisdictions adopt
Last checked: September 2026. Formulas are the standard building-science and code relationships; default thresholds are common international values and should be replaced with the ones in your code.