Bathroom scales - the type you are talking about when referring to your own weight - do actually measure weight. So the truth is a little more complex than other answers have pointed out.

What we should say when a bathroom scales gives your "weight", as say 70 kg, is that your weight is actually $70 g$ Newtons, where $g$ is the value of gravitational acceleration that is assumed in the calibration of the scales.

If you want to accurately estimate your mass, then you need to know what value of $g$ was assumed, and the local value of gravity $g_0$, since your mass is actually $70 g/g_0$ kg.

The local gravity across the Earth's surface varies by as much as 0.5% and so the scales, unless re-calibrated would report your "weight" as varying by 0.5% in sympathy with this variation. Similarly the "weight" reported by the scales if you went up and down in a lift would vary.

Note that this discussion refers to spring or stress-gauge balances. If you measure "weight" using something like an old-fashioned pair of scales or a beam balance, then you are directly comparing your mass against a test mass in the same gravitational field. Therefore this method of "weight" measurement tells you accurately what your mass is directly (in kg) and to estimate your weight you would then have to multiply by the local value of gravity.

Bathroom scales - the type you are talking about when referring to your own weight - do actually measure weight. So the truth is a little more complex than other answers have pointed out.

What we should say when a bathroom scales gives your "weight", as say 70 kg, is that your weight is actually $70 g$ Newtons, where $g$ is the value of gravitational acceleration that is assumed in the calibration of the scales. Sometimes there is an adjustment to change this assumed value which could be calibrated if you had an accurate test mass that you could put on the scales.

If not, and you want to accurately estimate your mass, then you need to know what value of $g$ was assumed, and the local value of gravity $g_0$, since your mass is actually $70 g/g_0$ kg.

The local gravity across the Earth's surface varies by as much as 0.5% and so the scales, unless re-calibrated would report your "weight" as varying by 0.5% in sympathy with this variation. Similarly the "weight" reported by the scales if you went up and down in a lift would vary.

Note that this discussion refers to spring or stress-gauge balances. If you measure "weight" using something like an old-fashioned pair of scales or a beam balance, then you are directly comparing your mass against a test mass in the same gravitational field. Therefore this method of "weight" measurement tells you accurately what your mass is directly (in kg) and to estimate your weight you would then have to multiply by the local value of gravity.