How To A Measure Light Bulb

Whilst its key to note the LED measurement and light bulb temperature, it is also imperative that when buying new light bulbs for your light fittings that you select the right sized light bulbs. It may seem obvious but it can be overlooked! At Dusk Lighting we want you the pick the right light bulbs for your home and to make sure that they fit into their new homes, you’ll need to know how to measure a light bulb.

You may need to measure a standard light bulb and fluorescent tubes depending on the fixture, and we will guide you on how to do both.

When would you measure a light bulb?

If a light bulb has blown and you need to replace it with a brand new one, but the packaging for the previous bulb with the information on has long gone, it will be necessary to get a correct measurement. Updating your current halogen lights to LED lights may also be a time when measuring a light bulb is required.

How to measure a light bulb

To measure a light bulb in order to find a correct replacement, you’ll need a measuring tape or a ruler for an accurate reading. A material measuring tape will need to be held tightly. There are three parts of the light bulb to consider when it comes to measuring for a replacement bulb. The length, which includes the glass and metal element, the width of the glass, and finally the metal base part of the bulb.


It’s important to measure the length of the bulb’s height, rather than just the surface length. So place your light bulb on a firm surface and position your measuring device vertically against the bulb from the metal or plastic base to the top of the glass bulb itself. Get the measurement in millimetres and note this down.

When measuring a fluorescent tube light, it’s important to take your measurements from the pins at each end, rather than the length of the lighting tube itself, for a more accurate measurement. This is because the pins will be slotting into the actual fixture.


You’ll find that a lightbulb actually has a code which will determine its shape and diameter at the widest point – the width. Measuring the lightbulb at the widest point will allow you to get this measurement, but measuring at the widest point will depend on the design of the bulb itself. Some LED light bulbs will have the wider diameter in the middle of the bulb, or close to the end. You can easily find this out by simply moving your measuring tape and noting where it is widest.


There are obviously various types of light bulb bases on the market, from screw to bayonet designs, but regardless of this, we will want to measure it in millimetres like the length and width. The base measurements are also coded, so for example, a classic Edison screw base which measures 27mm will be referred to as E27. Measure straight across the bottom of the light bulb base. For pin type bases, just measure between the two pins for your base measurement.

Finally, at Dusk Lighting we would always recommend double checking your light bulb measurements to ensure that no problems arise when trying to install your new light. Confirm and note down the length, diameter and base measurements of your light bulb and keep it at hand when purchasing a replacement bulb.

In our light bulb department you’ll find a wide selection of various bulbs to suit any light fitting. So whether you’re searching for the right bulb to fit in your lounge lights or bedroom lights, you’re bound to find what you’re looking for! Contact us if you’d like any more guidance on how to measure a lightbulb and we’ll be happy to help.

Comments are closed here.