Depends on the breed and on the individual bird. I have some pullets that started laying at 20 weeks (production breeds). I have others that have waited until 7 months. One of my Delawares laid at 23 weeks and the other just started laying at 26 weeks. Be patient, usually the longer they wait the bigger the pullet is and the healthier the eggs.
At least that's what I tell myself to make the wait a little easier.
They are usually, depending upon breed and health and their own internal little hormonal fluxes, ready to lay eggs anywhere from 18 weeks to 35 weeks.
The amount of time it takes to put an egg together inside their bodies is around 25 or 26 hours. That's why they normally lay the next day's egg about 2 hours later in the day, progressing in that manner until it's too late to lay an egg, and they lay it the next morning. That's for the regular layers... not all chickens are daily layers. But the amount of time to "create" an egg for laying is the same.
The longest amount of time is expended in creating the shell: about 19 hours! It's the last step in the process before the "bloom" is deposited on the shell and the egg is layed.
Because the egg is already "built" inside the hen, when she does stand up to lay it (regardless of where she's laying it), it will take less than a minute for the completed egg to be deposited outside of the hen's body.
Some hens like to make a little ceremony of it and sit in the nest for a couple of hours, resting up before the big push, and afterwards.
Other hens jump in, lay the egg, squawk the Egg Song - or not - and then jump right back out of the nest again.
Thanks all for the info! New here... I wanted to know how long between cracking out of the egg til laying one of one's own! Have a RI red - one of seven various hens - who is giving us a little brown egg every day. They all came to live with us in early May and she's the only one! All are healthy and seem so very happy. All wander the yard for a few hours a day. Eat well. One egg a day...Seven hens.. those first few eggs are sure expensive!: