My luggage is allowed to be 50 lbs each bag, and I'm not sure how much it weighs. Is there any way to weigh it with an accurate weight?
An ordinary bathroom scale should be accurate within a pound or two. If you have a digital scale that won't register such small weights, then weigh yourself, weigh yourself holding the suitcase, and subtract.
If you are away from home or don't have a bathroom scale, pharmacies often have a scale inside the store that you can use, either for free or by depositing a small coin.
As Alexander commented, dedicated luggage scales work well too. The advantage this has over a bathroom scale is that a suitcase or duffel bag may cover the readout. In addition, it might be more accurate.
While humans (at least me) are usually quite bad at estimating absolute weights, they are much better at comparing weights (at least in a certain range). Thus, if you lack an appropriate scale, you can get a good estimate if you hold your luggage in one hand and something that roughly weighs the maximum allowance in the other and estimate which one is heavier.
Now you only need to find something with known weight, to which purpose I usually employ:
- Bottles, cartons and other containers of beverages, which all weigh 1 kg/ℓ (excluding highly alcoholic beverages and beverages in heavy containers). There is some simple volume–weight relation in other unit systems too.
- Packs of sugar, flour, etc.
- Cans of food.
Note that the comparison is best if you pack all of those into a container which has a comparable handle to your luggage, e.g., a tote bag or a one-handle basket.
I usually try to travel with a travel scale. They are not that expensive (if you buy them at the right place) and can save you some headaches. Unfortunatly sometimes I forget it. What I allways usually do is weight the luggage at home (a WC scale is enough like Nate already sugested). That gives me an estimate for the return (pf how much more weight I can bring back).
Sometimes I just use the scale at the airport. If you put your luggage in a luggage belt at an unused counter that gives you the weight in the display. These are usually working. Of course that might be too late, but most of the times, if you already have good estimate, it's just enough to rearrange some luggage - wear an extra coat :) or move some stuff from the check-in luggage to the hand luggage, to be on the right weight. It's much better to do it in advance than while doing the check-in.
With some scales, its hard to set the luggage on the scale and get an accurate weight. So I get the scale by myself, and note the weight. Then I get off, let the scale reset, and get back on holding the piece of luggage. Then just subtract the two numbers.
(This also works well for weighing pets.)