An index-based calculator can provide only a broad brush valuation at individual property level. Specifically, our illustrative House Price Calculator (HPC) shows only the change in value of a house assuming that the house price inflation, applicable to the house type and to the county/London borough in which it is situated, is applicable to the property concerned.
The result is illustrative because the calculations are not done at postcode, street or even town level. Our illustrative HPC is built, like the LSL Acadata HPI, from Land Registry (LR) data and designed to provide closely accurate valuations for property portfolios, at which level individual variations are largely ironed out.
Whilst an accurate value for an individual house requires the engagement of a professional surveyor, as a guide to house price inflation, illustrative HPC has the advantage of using the true smoothed LR prices from 2000 (as opposed to mortgage offer prices) and monthly county/London borough data (as opposed to say quarterly, regional, data), and every transaction in England & Wales (as opposed to a sample). Note that, in months when county/London borough transaction volumes fall below the minimum number we require for accuracy, illustrative HPC employs price changes at the appropriate regional level.