Insulated Water Bottle Specs: Capacity, Vacuum Walls, Lids and Materials
An insulated water bottle listing reads like a list of numbers and badges: a size in ounces, “double wall” or “triple layer,” “vacuum insulated,” a lid name, “BPA-free,” “18/8 stainless” and a dishwasher line. This explainer goes through what each one tells you and what it leaves out, using the Owala FreeSip 24 oz as the worked example.
How we wrote this: Owala details come from the Owala FreeSip product page, including its features list, product details and FAQ, read in October 2026. Background on plastics and food contact rules comes from the FDA’s pages on packaging and food contact substances and BPA in food contact applications. Where Owala does not state a spec, we say so. Conversions marked as ours are simple arithmetic. We did not test the bottle.
The short answer
Read the size as the bottle’s total volume, not what you will pour out. Vacuum insulation between two steel walls is what keeps drinks cold. Pick a lid by how you like to drink and how much cleaning you will put up with. Treat “BPA-free” and “18/8 stainless” as statements about materials, and check the maker’s care page for which parts go in the dishwasher and which drinks the bottle is not meant for.
Step 1: Capacity in ounces vs what you can use
Bottle sizes are given in fluid ounces. Owala sells the stainless FreeSip in 24, 32 and 40 oz sizes, plus a 25 oz version in Tritan plastic. By our arithmetic, 24 fl oz is about 710 milliliters.
The number on the label is the bottle’s capacity, and the amount you actually drink from a full bottle is usually a little less:
- Headroom: you need a little space below the lid to close it without spilling.
- Ice: ice takes up room, so a bottle full of ice and water holds less water than its rating.
- Straws and spouts: a built-in straw sits inside the bottle and takes a small share of the space.
Owala does not state a usable volume for the FreeSip, so we do not give one. If the exact amount matters, fill the bottle as you normally would, then pour it into a measuring jug or weigh it on a kitchen scale. Our kitchen scale specs explainer covers how to tare a container first.
Size also changes the shape. Owala lists the 24 oz bottle at 10.68 inches tall and 3.12 inches across, and the 32 oz at 10.66 inches tall and 3.43 inches across. A wider base can be the difference between fitting a car cup holder or not, so check the diameter as well as the height.
Step 2: Single wall, double wall and vacuum insulation
- Single wall: one layer of steel or plastic. It is light, but the outside takes on the temperature of the drink, so a cold drink warms quickly and the bottle sweats.
- Double wall: two layers with a gap between them. If air is left in the gap, it slows heat transfer a little.
- Double wall vacuum: the air is pumped out of the gap. With almost nothing to carry heat between the walls, the drink holds its temperature far longer and the outside stays dry.
Owala describes the FreeSip as triple-layered and vacuum-insulated stainless steel. “Triple layer” is the maker’s own description of its construction; the page does not break down what each layer is. Owala says the bottle keeps drinks cold for 24 hours. That is the brand’s figure, and like any cold time it depends on the starting temperature, how full the bottle is, how often you open it and how warm it is around you.
Step 3: Lid types, straw, chug and sip
The lid shapes how you drink and how much cleaning the bottle needs:
- Straw lid: drink upright through a straw. Easy to use on the move, but the straw needs regular cleaning.
- Chug lid: a wider spout for big gulps, usually with a flip cap.
- Sip or screw cap: a small opening or a plain cap. Fewest parts, but slower to drink from.
The FreeSip combines two of these. Owala says you can hold it upright to sip through the built-in straw, or tilt it back to swig through the wide-mouth opening. The lid opens with one push and locks with another, and Owala says the carry loop also works as a lock when closed. Owala calls the lid leak-proof. The page also lists a wide opening for cleaning and adding ice.
More moving parts mean more places to clean. Owala says the bottle is designed to be quick and easy to take apart, with minimal hard-to-reach surfaces.
Step 4: Dishwasher-safe parts
“Dishwasher safe” often applies to some parts and not others, so read the care line closely. Owala’s FAQ says the stainless FreeSip lids are top-rack dishwasher safe and the straws can go in the silverware bin. It says the cups are also technically dishwasher safe but strongly recommends hand-washing them. Its feature list sums this up as a dishwasher-safe lid and a hand-washable cup.
Whatever the bottle, take the lid apart as far as the maker allows, wash the straw and spout, and let the parts dry before you put them back together.
Step 5: What the bottle is not for
Many insulated bottles have limits on what goes in them, and the FAQ is where to find them. Owala says the stainless FreeSip shouldn’t be used with hot, carbonated or perishable liquids, and points to its tumbler products for hot or carbonated drinks. Check the care guide for any bottle before you fill it with something other than water.
Step 6: BPA-free and 18/8 stainless wording
BPA-free. BPA is an industrial chemical that, per the FDA, is used to make polycarbonate, a hard, clear plastic, and is also found in epoxy resins that line some metal food and beverage cans. On a water bottle, “BPA-free” tells you the plastic parts are not made with BPA. It describes materials, not a test result. The FDA also notes that substances that can migrate from packaging into food are subject to premarket approval as indirect food additives or food contact substances. Owala lists the FreeSip as BPA-free, lead-free and phthalate-free, and describes its plastic parts as BPA-free Tritan.
18/8 stainless. The numbers refer to a stainless steel with about 18% chromium and 8% nickel. The Owala page we read describes the FreeSip as stainless steel but does not give a grade, so we do not add one. If a listing names a grade, it is the maker’s statement about the steel; if it does not, ask the maker.
A quick checklist
- Read the size as total volume, and leave room for ice and the straw.
- Check height and diameter against your cup holder and bag.
- Look for vacuum insulation if you want cold drinks to stay cold.
- Pick a lid by how you drink and how much cleaning you will do.
- Read which parts are dishwasher safe and which drinks are not allowed.
- Treat “BPA-free” and steel grades as material statements from the maker.
FAQ
How much does a 24 oz bottle actually hold?
About 710 milliliters by our arithmetic. Ice, headroom and a built-in straw leave you a little less to drink.
Can I put coffee in the Owala FreeSip?
Owala says the stainless FreeSip shouldn’t be used with hot, carbonated or perishable liquids.
Is the whole bottle dishwasher safe?
Owala says the lid is top-rack dishwasher safe and the straw can go in the silverware bin, and it strongly recommends hand-washing the cup.
Where to go next
For more everyday basics, see our kitchen tools buying guide or browse all kitchen tools. For another prep tool read spec by spec, see our salad spinner specs explainer.