Southwest is known for not charging passengers to check two bags each, but like many other airlines, if your bag weighs more than 50 pounds — even by as little as half a pound — be prepared to pay up.

If your bag weighs 51 pounds, it will cost you $150.

Over 70 pounds? $200.

And other airlines?

If your bag is over 50 pounds but under 70 pounds on a domestic flight, American Airlines charges you $40. Over 70 pounds: $100.

Many travelers weigh their bags at home before heading to the airport, but if you’re close to being over, make sure there’s enough room in your carry-on bag to carry an additional two to five pounds.