Weight is a force, so it is measured in newtons using a newtonmeter, also called a spring balance. A newtonmeter has a spring inside it, a hook at the bottom and a scale marked in newtons.
To measure the weight of an object, hang it from the hook. The spring stretches until its upward pull balances the weight of the object, and then the object hangs at rest. The pointer stops at a mark on the scale and you read the weight in newtons. The greater the weight, the greater the stretch of the spring.
Do not confuse this with finding mass. Mass is measured in kilograms using a balance. A balance reading in kilograms is giving the mass, not the weight. Because the pull of the spring is equal to the weight when the object is at rest, the newtonmeter reading is the weight.
