RAPID WEIGHT GAIN

You're probably retaining water and are bloated. The 1 pound of fat is usually equally distributed and, if I'm correct, takes quite a while to travel to parts of your body. Drink TONS of water over the next few days and you'll be fine.

I am not a health professional, but I would say its mostly water weight from a high sodium intake. Make sure you drink plenty of water to flush it out off your system and try again.

your body changes everyday, all throughout the day.. u always want to make sure you measure first thing in the am before youve ate or drank... after using the rest room
if ur already doing that, then you could def be holding water weight, especially if u went over salt... so drink alot of water...like 15 cups, per day. Also, i hate measuring because if you hold the tape any tighter or looser, or even a couple cm off from the first position you measured in, it changes everything.

3500 calories is 1 pound... this would need to be 3500 over your daily bmr. (so if ur suppose to eat 1200 a day, youd need to eat 4700 to gain a pound)

yup i know this, i probably have eaten 4700. how long for that pound to convert

8-48 hours, depending on how fast the food travels through your digestive system. As others have said, you will have a lot of water retention as well.

Overeating by that much in one day, especially given that your current goal weight will leave you underweight, is concerning. Sometimes we binge because it was a party and we weren't paying attention, sometimes because we've been starving ourselves for too long and it catches up to us, sometimes for complex emotional reasons, and sometimes because we're literally addicted to the temporary good feeling a binge produces. I hope you are able to examine your reasons for this particular binge and use it as a learning experience.