How to Calculate Mass & Weight

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In everyday life, people tend to think of weight in terms of how heavy something feels. In physics, however, weight has a more specific meaning. It refers to the amount of force gravity exerts upon an object. What most people ordinarily call weight is called mass in physics. Mass refers to the amount of matter in an object and is measured in kilograms. To calculate the weight of an object, you need to know its mass.

Finding Mass

    Slide all three weight poises on the triple-beam balance all the way to the left. If the pointer is not aligned with the zero line, slowly turn the zero balance knob to adjust it.

    Place the object on the balance plate. The pointer moves to the left of zero. Slide the heaviest weight poise until the pointer moves to the right of zero. Slide the heaviest weight poise back until the pointer moves back. For example, when you move the heaviest poise to 300, the pointer moves to the right of zero. Slide the heaviest poise back to 200 and start sliding the middle poise.

    Repeat the procedure with the middle and lightest weight poises.

    Add the numbers underneath each weight poise on your calculator. The total is the mass in grams. For example, the heaviest poise reads 200, the middle poise reads 30 and the lightest poise reads 0.3. The total mass is 230.3 g.

    Write down the mass and use it to help you calculate the weight of the object.

Calculating Weight

    Convert the mass from grams to kilograms by dividing the mass of the object by 1,000. For example, an object with a mass of 230.3 g would have a mass of 0.2303 kilograms.

    Write the formula for weight on your paper: w = mg. W stands for the weight of the object, m stands for the mass of the object, and g stands for the gravitational constant On Earth, g always equals 9.8 meters per second per second. According to, a website about physics, this can also be written as 9.8 newtons/kg.

    Calculate the weight using the formula and your calculator. For example, if the mass of an object is 0.2303 kg, w = 0.2303 kg x 9.8 newtons/kg, or 2.2569 newtons.


About the Author

Jack Ori has been a writer since 2009. He has worked with clients in the legal, financial and nonprofit industries, as well as contributed self-help articles to various publications.

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