Free Home Renovation Budget calculator with clear step-by-step results.
Builds a renovation budget from a rate per square metre set by specification level, adds structural work as a separate lump sum, then layers professional fees and contingency on top - in that order, because fees are a percentage of construction and contingency has to cover both.
Construction cost
Cost = area x rate for the specification level + structural work
Total budget
Total = construction x (1 + fee rate) x (1 + contingency)
Indicative budgeting only. Renovation work may require planning permission, building control approval and party wall agreements, and costs vary widely with condition, access and location.
Because overruns generate extra design and supervision time too. Applying contingency to the combined figure covers both consequences of a change.
They are order-of-magnitude planning figures and vary by two or three times between regions and between a cosmetic refresh and a full strip-out. Replace them with local quotes as soon as you have them.