These special weights are used to calibrate weighing equipment. It is important that all equipment used to measure and weigh is effectively calibrated frequently. By doing this, it can be ensured that the readings they give are accurate.

So, if you want accurate weight measurements from your scales or balances, they need to be calibrated. To calibrate them you need to use weights – which are called Calibration Weights!

Ordinarily, the weights will be brought to site by the calibration service that work on your equipment, such as Calibration Lab. If you’ve never seen the weights before – or perhaps even if you have – you may not appreciate there is more than meets the eye when it comes to these very special sets of weights – and what they are used for.

Are they Special Weights?

In many ways, yes they are! For example, high quality, professional grade calibration weights will be constructed from a metal with low magnetism. That way, the latent magnetic fields won’t affect the mechanisms and workings of the scales and balances during the calibration process.

This is just one example of the lengths that calibration companies will go to ensure as accurate a weight calibration as possible. Another example is in the incredible accuracy in the actual weight of the calibration weights – something we discuss below!

Different Materials & Sizes

The types of weights used for calibrating scales and balances come in quite a range of materials, shapes and sizes. Each material has strengths and weaknesses, making each one more suitable for use in different applications.

Amongst the materials used to make calibration weights are:

Cast Iron

By far the most common material used in these weights, especially at higher weight ranges (i.e. over 1 kilogram). In fact if you hire a calibration company to work on your scales and balances, there is a very good chance that they will use cast iron weights. They are very robust and last for a long time – provided however that they are stored and used in a dry environment.

Because of that reason, these types of weights will typically be found testing scales and balances in Industrial, Commercial and Retail settings.


These weights are typically available in a weight range from 1 gram up to 10 kilograms.

Brass is a softer material than the cast iron used in the weights we discussed above. This can mean that they are more prone to scuffs and damage and have an overall shorter lifespan than the very hardy cast iron models.

They do however have one big advantage over Cast Iron that is the fact they do not rust. You will therefore most likely find these weights being used to calibrate scales and balances found in food factories or places where there could be a high level of moisture in the air.

Stainless Steel

Finally, stainless steel is very much considered the premium material for making the very best weights.

This is because they combine the toughness of cast iron with the ability to handle moisture that is the hallmark of brass weights – so they literally provide the best of both worlds!

It is also the most expensive material, so will often be deployed only as smaller weights for calibrating highly accurate scales and balances such as you would find in a laboratory setting for example.

Are they accurate?  

Oh yes – very much so in fact!

Calibrated weights are typically adjusted on a scale of accuracy with a variation of 0.005%.

In real terms, that means that a calibrated weight of 20kg with a M1 rated accuracy will weight exactly 20kg, with a margin of error of just a single gram.

It is this accuracy that makes these types of weights truly special – and uniquely suited to the task of calibrating weights and scales.