Calculating Radiator Pipe Centres & Maximum Width of Radiators

We always recommend waiting until your cast iron radiators are onsite before fixing pipework, because cast iron is not an exact product and each radiator is hand assembled there will always be slight differences between each radiator.

However, we understand that sometimes you’ll need rough measurements for first fix prep. If that’s the case, follow this method to estimate your pipe centres:

1. Use the Valve Specification PDF

Each of our radiator valve sets includes a technical drawing in the product download section. This shows the distance from the thread on the valve tail to the centre of the valve.

Then add this measurement twice (for both sides) to the width of your radiator to calculate the approximate pipe centres.

Example:

If you’re using a Kenilworth Thermostatic Valve Set (which measures 45mm from thread to centre) on a 10-section Traditional Victorian radiator measuring 650mm wide, the approximate pipe centre width would be:

650mm + 45mm + 45mm = 740mm

2. Estimating From the Wall or Skirting Board

To estimate the distance from the wall or skirting to the pipe centre, we recommend:

Half the radiator’s total depth + 10mm (minimum)

This allows for pipe alignment when radiators are fitted

3. Calculating the Space Needed for Valve Operation

If you need the minimum width required to freely operate the valves (e.g. in a tight alcove or recess), use the following guide:

Radiator width + ~150mm (or ~6 inches)

This gives you a rough outside valve to outside valve clearance—but be aware this can vary slightly depending on the valve style you choose.

All measurements provided by Cast Iron Radiator Centre, are approximates, and the examples above are for a guide only. If you are in any doubt please contact our friendly team, who’ll be more than happy to help make sure that the radiators that you purchase will be right for your space.