@Richard Kay the federal housing finance agency, fhfa, has a hpi calculator. Put the quarter you bought your house in 1995 and 100k as purchase price. Then enter the value quarter eg., 2018 q1. Find the percentage gain...if 2018 value is 150k then the gain is 50%. Work backwards. This will give you a ballpark. Not sure what the margin of error is but the site might supply that.