There are so many baggage restrictions on airlines now, every trip requires a little research and a lot of weight-conscious planning. Putting your luggage on a scale before you get to the airport is always a good idea. If your scale requires skin-on-scale contact (many of the digital readout ones do), try this:
Get on the scale and weigh yourself. Get off the scale. Get back on the scale holding your luggage. Subtract your starting weight from your weight with the luggage to figure out how much the luggage weighs. If it's less than the baggage restrictions of the airline you're flying, you're good to go!