Shampoo Bars vs Refillable Travel Bottles: Cost per Wash and Airport Liquid Rules

The short answer

A shampoo bar is a solid, so it stays out of the liquids bag on every route. That is its main advantage. A refillable silicone bottle lets you bring the shampoo you already use. The catch is that it counts toward liquid limits, and a 100 ml bottle holds only about ten washes at a typical dose.

Based on the prices we looked at, the two cost about the same per wash. Your choice comes down to three things: how long you will be away, whether you only carry a cabin bag, and how much you care about keeping your usual formula.

What airports allow in your cabin bag

In the US, carry-on liquids fall under the TSA's 3-1-1 rule. Each container can hold 3.4 oz (100 ml) or less, and all of them must fit in one clear quart-sized bag, one bag per passenger. A guide from luggage maker Away, published in April 2026, lists solid shampoo bars among the items that can go anywhere in a carry-on with no size limit. The same guide says checked luggage has no liquid size limit. It also says an oversized liquid found by accident is confiscated, not fined. The TSA's own site would not load for us, so check tsa.gov before you fly.

The UK is in the middle of a change. Which? reported on 23 January 2026 that liquids can now stay inside cabin bags at all UK airports. It also said most airports, but not all, allow containers up to 2 litres. Which? named Heathrow, Gatwick, Edinburgh, Birmingham, Bristol, Belfast International and Belfast City as having dropped the 100 ml rule. Luton and Manchester still had the 100 ml limit at the time. Which? also warned that the airport you fly home from may not have the new scanners, so a bottle allowed on the way out may be refused on the way back.

Across Europe, 100 ml is still the default. On 30 January 2026, Euronews listed airports allowing up to 2 litres, some only in certain lanes or terminals: Dublin, Rome Fiumicino, Milan Linate, Prague Terminal 2 and parts of Munich, Frankfurt and Berlin. Paris, Madrid, Lisbon, Athens and Marseille were still at 100 ml. Brussels said it had no concrete plans to change its equipment. Euronews also reported that the European Commission said in July 2025 that dropping the rule across the bloc was in the pipeline. We found no sign that this has been adopted.

• Shampoo bar: outside liquid limits under the TSA rule, as Away describes it, and a solid everywhere else

• 100 ml bottle: allowed in carry-on at every airport covered here, but it uses space in your liquids bag where 100 ml still applies

• Bottles over 100 ml: only at airports with the newer scanners, and the return airport may differ

What each costs per wash

Bar: Canadian retailer Well.ca listed Ethique's 110 g Minimum Unscented shampoo bar at around CAD $22.46 in November 2026. Ethique says its bars last more than 80 washes on average, based on a survey of 4,865 customers. That works out to about CAD $0.28 per wash. Ethique also says a bar is equivalent to three 350 ml bottles of liquid shampoo. It adds that lifespan depends on how often you wash, how much you use and whether the bar dries between uses.

Bottle: You pay for the shampoo inside and for the bottle itself, once. Head & Shoulders' UK site suggests about 10 ml per wash for most women. It says longer, curly or thicker hair needs more, and short or fine hair less. At that dose, a 370 ml Head & Shoulders Classic Clean shampoo listed by Well.ca at around CAD $9.99 in November 2026 gives about 37 washes, or roughly CAD $0.27 each. If you decant a salon shampoo, the cost per wash goes up with its price.

Humangear lists its GoToob+ three-pack, which includes small, medium and large bottles, from around US$23.99 in November 2026. That is a one-time cost, and it shrinks the more trips you take. A bar needs no container, though many people buy a tin or case for it.

Capacity: how many washes fit in your bag

Humangear lists the GoToob+ in three carry-on sizes: Small (1.7 fl oz), Medium (2.5 fl oz) and Large (3.4 fl oz, the 100 ml maximum). It describes them as TSA-approved for carry-on. At about 10 ml per wash, the Large holds around ten washes, the Medium about seven and the Small about five. Under a 100 ml rule, a Large bottle of shampoo also shares one quart bag with your toothpaste, conditioner, sunscreen and anything else liquid.

A single bar claimed to last more than 80 washes covers a far longer trip than any carry-on bottle, and it leaves the liquids bag for other things. Ethique also sells mini bars for short trips.

Leaks, wet bars and other practical points

Bottles: Humangear says the GoToob+ has a locking cap (LoopLock) and is made from silicone with a polypropylene cap. The product page we read makes no leak-proof claim. A bottle keeps your usual shampoo, which matters if you use a specific formula on a dermatologist's advice. Keep using that product rather than switching for a trip, and ask a professional before changing anything prescribed.

Bars: Water is the main problem. Ethique says keeping a bar dry between uses makes the biggest difference to how long it lasts. It recommends a drained, ventilated tray or a sisal bag that can dry out, and warns against leaving the bar in standing water. A wet bar packed straight into a closed tin soon after a shower is the typical failure on the road. If you are checking out right after washing, plan to let it air-dry or carry a draining case.

Retailer directions for the Ethique bar are to wet your hair fully, rub the bar over your roots several times, set it down, then work the lather through and rinse. If you have never used one, try it at home first so you know how your hair reacts before a trip.

Which one to pack

Both options cost about the same per wash at mid-range prices. The real differences are capacity, liquid rules and convenience.

• Pick a shampoo bar if you travel with only a cabin bag, take trips longer than about a week, fly through airports still at 100 ml, or want the liquids bag free for sunscreen and skincare.

• Pick refillable bottles if you rely on a particular liquid formula, take short trips of five to ten washes, check a bag anyway, or check out early and do not want to pack a wet bar.

• Pack both if you want conditioner or a backup: a bar for shampoo and one 100 ml bottle for conditioner keeps you within the limits at every airport covered here.

Sources

• TSA Liquid Rules: What You Can (and Can't) Bring on a Plane – Away
• The UK's airport liquid rules for 2026 – Which?
• Liquid anxiety: Which European airports have scrapped the 100ml limit? – Euronews
• How Long Does a Shampoo Bar Last: Get the Facts – Ethique
• Ethique Bar Minimum Unscented Solid Shampoo – Well.ca
• Head & Shoulders brand page – Well.ca
• How much shampoo should you use? – Head & Shoulders UK
• GoToob+ 3-Pack – humangear