This is a tested carry-on-only list for women in a 35L bag for 2+ weeks in Italy. Your needs and preferences may vary, and that's perfectly fine. Just be aware of the possibility that any checked bags could get lost en route, and keep the absolute essentials (like medications and one change of clothes) with you at all times. You also need to be able to lift or carry all of your own luggage onto trains, so definitely test your capacity before leaving home.
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Important documents:
Passport (Legally required to always keep with you in Italy)
Debit card & travel credit cards (Tell bank about your travel dates)
Printouts of any tickets (unless it specifically says mobile entry)
Printouts of travel insurance
Photos of your regular health insurance card
Electronics:
"Type C" plug adapter, plus small extension cord or power strip
Phone charger, plus an extra USB-A adapter
Portable power bank with built-in cords
(Most hair tools need a converter and to be dual-voltage)
Clothes: (See important note below)
3-4 full outfits including socks
as many underwear as will fit in a 1-gallon ziploc
Thin pajamas
2 bras
1 warm jacket/blazer/sweater layer
Belt if preferred
Swimsuit if applicable
2 pairs of comfy shoes (alternate daily)
1 pair should be waterproof
Plus flip flops for hotel floors or beach
Toiletries and Cosmetics
Buy sunscreen, lotion, mouthwash, etc large liquids after airport security or on arrival
Meds, supplements, vitamins:
Daily routine pills sorted into 2x3 ziploc bags
Have photos of any prescription bottles
Motion sickness aids
Sleep aids (melatonin or Rx pills)
OTC meds for any unexpected GI issues
Any emergency pills stay in purse at all times
For plane ride:
Inflatable neck pillow
Earplugs & eye mask
Sanitizing wipes
Compression socks
Sea Bands if prone to motion sickness
Day pack items:
(Share one single lightweight backpack with your travel companions. Backpacks are less secure against pickpockets, so keep valuables separate.)
Thin rain jacket or disposable poncho
Tiny umbrella if forecast indicates
Disposable water bottle (reuse it the entire time)
Carabiner for the water bottle
Old fashioned folding fan (for all seasons)
Hand sanitizer
Nail clippers & TSA-approved pocket knife
Tide pen or Shout wipes
Picaridin mosquito wipes
Sunscreen
Sunglasses
Earbuds for audioguides
Camping toilet paper or kleenex
Disposable toilet seat covers
Gum, mints, or Listerine strips
Pen
Gloves and hand warmers in cold months
Laundry bag
Wash sack like Scrubba or a 2.5 gallon ziploc bag
Mini laundry detergent sheets
Miscellaneous
Body Glide for preventing chafing
Microfiber hair towel
Satin pillowcase
Tampons if needed
White noise app or device
Money belt or equivalent secure pouch
Extra ziploc bags of all sizes
Some bubble wrap for delicate souvenirs
An empty duffle bag in case you overdose on souvenirs
Pack a wide-brim hat or easily buy one on arrival
The real secret to packing light is to bring fewer clothes. Absolutely no one will notice that you're re-wearing the same 3-4 outfits over and over. The right fabrics don't need to be washed for a month! Yes, you read that correctly. Merino shirts and nylon travel pants just need to be hung up overnight to air out in order to smell fresh the next morning. But the most important feature of any clothing you bring is how fast it can drip dry overnight. You never know when a fork full of spaghetti will land in your lap, resulting in a necessary scrub in the hotel sink. After washing, wring it out, roll it up in a dry towel and wring again, then hang near some airflow in the room. Test your outfits before packing them. Jeans will almost always fail to dry, and they take up more cubic inches in a suitcase than most other pants. Many cottons will not only fail this test, but they absorb-- just like a cotton ball-- any sweat throughout the day and then dry slowly enough for stinky bacteria to multiply, resulting in too much odor to re-wear without washing every time. Most athletic gear is a good choice. The internet is full of great suggestions if you Google "minimalist packing tips." But merino shirts are also a favorite because they look less casual than your Under Armor gym shirts. They come in different weights for different seasons, and the thinnest are often blended with other great fabrics like tencel. Amazon sells several brands that are affordable. Don't forget to choose merino socks, too.