re: How long? Newborn size diapers.

Until the bag from the hospital ran out, so maybe a week. She was 7lbs 2oz.

DS was 8lbs 5 oz and was in size 1's for about a month!

i think maybe a month and a half. she was 6lbs 8oz when she was born.

I would stick with the one smaller box for now and buy more if you need to.

Quoting Jᴇᴢ:" My daughter is 4 weeks, and just starting to outgrow newborn size 1, though some brands are different ... [snip!] ... (the pampers still fit her, the huggies don't) and we're moving onto newborn size 2. She was 9lbs 7 when she was born."

I've always used Pampers and it goes NB, size 1, size 2, etc.
I've never heard of NB size 1 and NB size 2.

Quoting ☮Scarlet Begonia:" How long was your baby in newborn diapers? I can't remember how long my son was. Also what was their birthweight?"

8 lb3 oz.
and newborn for 5 1/2 weeks

about 1 week and he was 7 lb 4 oz. I bought 1 50 bag after ones from hospital ran out and he was peeing through them

#1 10lbs-never
#2 9lbs-1 small pack

I just switched to 1's
He's 5 weeks old. 6 lbs 14 oz at birth.

Quoting ☮Scarlet Begonia:" I've always used Pampers and it goes NB, size 1, size 2, etc. I've never heard of NB size 1 and NB size 2."

In America maybe it does, sure.
They do 3 'new baby' sizes here.
http://www.boots.com/en/Pampers-New-Baby-Size-1-Carry-pack-25-Nappies_1051485/
http://www.boots.com/en/Pampers-New-Baby-Size-2-Carry-Pack-33-Nappies_1051487/
http://www.boots.com/en/Pampers-New-Baby-Size-3-74-Nappies_1210708/

Similarly huggies do newborn size 1, 2 and 3;
http://www.boots.com/en/Huggies-Newborn-Size-1-Carry-pack-27-Nappies_118522/
http://www.boots.com/en/Huggies-Newborn-Size-2-Economy-Pack-62-Nappies_955844/
http://www.boots.com/en/Huggies-Newborn-Size-3-Economy-pack-54-Nappies_955846/

Quoting Jᴇᴢ:" In America maybe it does, sure. They do 3 'new baby' sizes here. http://www.boots.com/en/Pampers-N ... [snip!] ... http://www.boots.com/en/Huggies-Newborn-Size-3-Economy-pack-54-Nappies_955846/"

I used the huggies size 1's! I think I went through like 8 packs before we bought size 2's.

My 3 week old is still in them. He was 6 and 5 at birth. Just barely started fitting into cloth (gdiapers.)

Less then a week. 8.2 pound