Years ago, when I was just beginning arctic travel, my partner and I showed up at the airport with 12 pieces of luggage for a two-month expedition. The airline clerks seemed interested in our project and checked in all our gear without any fees. Good luck that happening today.
Even if you don’t present yourself at the counter with a small mountain of gear, you risk being charged or having to frantically withdraw items if you’re just a couple of pounds overweight. Obviously, it’s best to know if your luggage passes muster before leaving home. Ordinary bathroom scales give a rough figure but aren’t particularly accurate.
Another traveler once showed me his medical-quality digital scale. I fell in love with it, immediately bought one and use it every time I travel. It’s accurate to 1/10 of a pound (or kilo; you can choose either unit). It really does measure those fractions accurately. Often, I show up at the airport with a suitcase that weighs exactly 49.9 or 69.9 pounds, right on the limit. I’ve never had problems; some check-in staff have even commented how the luggage comes in right on the nose.
My older scale cost $100, and the new model is the same. Mine has a rather low weight limit, so I can’t both stand on the scale and hold a heavy duffle. But there is a workaround: If you stand on this scale, then turn it on, rather than vice-versa, it reads zero with you on it. Then you pick up the luggage, and a reading appears. This is how you get an accurate weight for a soft piece of gear, like a duffle, that doesn’t fit properly on a scale. The current model of scale measures up to 200kg, so you shouldn’t need a workaround.
As a bonus, such a precise device keeps tabs reliably on both your own weight, and your pet’s.