The Short Answer: way too much.
The Longer Answer: see below.
[thanks to DT reader and new dad Bruce]
Related, in a ripped off kind of way : What's in Your Gadget Bag, Glenn Fleishman? [homage/apologies to Gizmodo]
First off, we almost never empty our diaper bag, just keep refilling it. So who knows what's accumulated in there the last 10 months? Diapers (4 Pampers Cruisers; we usually go out with 6-8)
Wipes (A Huggies plastic case stuffed with Costco wipes, the best)
Changing pad (came with the bag)
Two books (My First ABC board book, Hello, Spot! soft book)
Cloth diaper that someone decorated with a cutesy pink edge
Flannel burp pad my mother made a million of for us
One complete change of clothes: one-piece footed pajamas is the easiest.
White Baby Gap cable knit cap, which the kid refuses to leave on her head.
Plush bunny rattle on a Velcro wrist strap (Velcro=very good to chew on, apparently)
Tiny rubber duck
Chillable figure-8 teething ring
Collapsible brush/mirror my wife got as a Clinique bonus
8-oz. First Years disposable cup of Cheerios (yes, we've gotten to the Cheerios stage)
One formula dispenser from Especially For Baby (white lid, not the leaky blue one)
Three 4-oz. travel packs of Enfamil Lipil formula
Two Ziploc sandwich bags, empty
One Ziploc sandwich bag with half a rice cake in it
One Bibster disposable bib
Four (??) First Years disposable spoons (So that's where they went.)
One Medela Quick Clean micro-steam bag for sterilizing a bottle in a microwave
One Bib'evian adapter for making a bottle out of Evian (we were happy to have it the one time we've used it)
Mylicon gas drops
Tylenol infant drops
Tiny travel bottle with baby shampoo
Tiny travel bottle of Purell Hand Sanitizer
Three anti-bacterial Wet Ones
Children's Oral-B toothbrush (Label: "NOT for chewing." The Kid: "Forget that, I can't even read yet.")
Tic-tac-sized pillbox full of OTC painkillers
One Clinique lipstick, Black Honey (Ahem. This is not a purse...)
One black plastic old-man comb, bought to deal with cradle cap
Tiny Bugaboo-logo Vaseline tub (from the maintenance kit)
Three California Baby tubs: sunscreen, moisturizer, diaper cream (I was told to point out these are all very small.)
What's not in there, but usually is: Two Playtex Ventaire bottles with filtered water (not bottled; gotta get that flouride)
One or two jars of food
wife's cell phone (Sorry, just callin' it like I see it.)
Unread New Yorker, any date--they're all unread
Conclusion: There's probably way too much stuff in here. But as soon as you pare it down, your three-hour tour'll unexpectedly turn into a day-long adventure, and you'll be screwed.