Work out loft conversion value instantly with clear inputs, formula shown and shareable results.
A loft conversion adds habitable area at the local value rate, discounted about fifteen percent because loft rooms with sloping ceilings and dormer windows are valued below main floor space. Netting total cost including planning and fees against that uplift gives the real gain, which depends heavily on the local rate per square foot.
Value added
Added = habitable area x local rate x 0.85 loft discount
Return
Return = (value added - total cost) / total cost x 100
Added = habitable area x local rate x 0.85 loft discount. A loft conversion adds habitable area at the local value rate, discounted about fifteen percent because loft rooms with sloping ceilings and dormer windows are valued below main floor space.
Where the local rate per square foot is low relative to build cost, or where the conversion removes the only storage and needs an awkward staircase that sacrifices a bedroom below.
This calculator takes 4 inputs: Conversion cost, Habitable area created, Local value rate, Planning and professional fees. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.