Pick a door and width, fetch your local weather, and we’ll estimate how much it will expand or shrink today.
Or custom
Tap a size above or type a custom width.
Used to suggest a safer gap today if the door is likely to expand.
Tip: click “Use my location” to auto-fill temperature and humidity.
The Door Expansion Calculator is a professional tool designed for carpenters, joiners, and door installers who need to understand how environmental conditions affect door dimensions. Wood and composite doors expand and contract with changes in temperature and humidity, which can affect fitting and gap requirements.
Our door expansion calculator uses advanced formulas to estimate how much a door will expand or shrink based on current temperature and relative humidity. The tool supports multiple door types including hollow-core interior doors, MDF/HDF fire doors, solid oak doors, and solid wood fire doors. You can automatically fetch your local weather conditions or enter them manually.
Explore our other professional construction calculators: Architrave Calculator for door trim measurements, Angle Calculator for perfect miters, Spindle Calculator for balustrade spacing, and Wallplate Square Checker for framing accuracy. Visit our apps directory for more free construction tools.
The door expansion calculator is trusted by UK construction professionals for accurate door fitting guidance. Understanding how doors will expand or shrink helps installers set proper gaps, preventing binding in summer or excessive gaps in winter. This tool is essential for professional door installations in varying climates.
For more information about door installation best practices, visit CITB (Construction Industry Training Board) or consult British Woodworking Federation for industry standards.