When buying a tape measure, it’s important to consider what class of tape measure is suitable for your project. The difference in class among various tape measures accounts for the difference in their respective accuracy.
To be clear, this classification of each tape measure primarily depends on their ability to follow the standards of accuracy tolerance and margin error. The EU weight and measures the classification of tape measures into grade I, grade II, and grade III.
If you are on your way to finding the most accurate tape measure, then this reading is for you.
Tape Measure Certification
If the tape measure is certified, it has the class printed on it and other symbols, including the length of the tape, year of manufacture, name of the manufacturer, and country. As for retractable tapes, Class I tapes are the most accurate ones, whereas Class II tapes are the most commonly available in the market.
Professionals abundantly require this type of tape measure because it offers an extra level of accuracy, which class II and class III type of tape measures do not provide. A class I tape measure is accurate to about ±1.10 mm over 10 m lengths.
That means, when you check the accuracy of a tape measure, per 10 meters, it has to fall between the numbers 9998.9 mm and 10001.1 mm. If it’s 9999 mm (off 1 mm only), it’s qualified as Class I. It’s not qualified as class I if it’s off of that range.
Most tape manufacturers make class II tape measure as a multi-purpose tape measure that is suited to a wide variety of daily applications. A class II tape measure should be accurate to about ±2.30 mm over 10 m lengths.
That means if your 10-meter-long tape measure is actually 9997.5 mm (off 2.5 mm), it’s surely not class II.
Class II tapes are easily accessible to the general users and do not lack far behind Class I tapes in terms of accuracy. So, they are preferred by industries and professionals for daily non-critical measurement tasks. This is why class III tape measures are less abundant than class I.
The Class III tape measure are responsible for the least level of accuracy in the measurements. Such tape measures are used in non-critical applications which do not require such high standards of accuracy in the results they provide. The accuracy provided by the class III tape measure is around ±4.60 mm over 10 m lengths.
Heat exposure may expand the tape material. This class allows a tolerance of ±4.60 mm. That means it’s only allowed to be off 4.6 mm either negative or positive of the 10-meter tape measure. If the tape’s length is 30 meters, and it’s off 12 mm, it’s still qualified as Class III.
The choice of each class of tape measure is purely dependent on the area of their application and the type of industry. For industries that are involved in manufacturing precision engineering parts and components, a high level of accuracy is important, and therefore Class I tapes are required. Whereas, as the level of desired accuracy decreases and cost-cutting increases, the user should shift towards Class II and Class III tapes that are more abundantly available and less costly.
If you are looking for the Class I tape measures, you can find them marked as Class I by the manufacturer. Unfortunately, this tape measure is not heavily available on the market. Some of them are Tajima H1550MW (5 meters) and Gatortape (14 feet).