Both keep your drink hot or cold. Both come in stainless steel. So what's the actual difference between a thermos and a tumbler, and which one should you grab on your way out the door?
The short answer
A thermos is a sealed, bottle-style vacuum flask built to hold temperature as long as possible and survive a ride in your bag. A tumbler is an insulated cup with a lid, built for easy sipping at your desk or in your cupholder. Thermos for all day on the move, tumbler for everyday drinking.
What is a thermos?
Thermos started out as a brand name, and it's now everyday shorthand for any vacuum-insulated flask. A thermos has double stainless steel walls with a vacuum between them, a narrow mouth and a screw-on lid, often with a pour spout or a cup that doubles as the cap.
That sealed design is what makes a thermos the champion of long hauls. It keeps coffee, tea and soup hot (or drinks cold) for many hours, and it can ride sideways in a backpack without leaking.
What is a tumbler?
A tumbler is a cup-shaped drink container with a lid. Today's insulated tumblers use the same double-wall vacuum construction as a thermos, so they keep hot drinks hot and cold drinks cold too. They're just built for convenience: a wide mouth for ice, a press-on or slide lid, often a straw, and a shape that fits most cupholders.
Curious how the insulation actually works? Here's the science behind insulated tumblers.
Thermos vs. tumbler at a glance
| Thermos | Tumbler | |
|---|---|---|
| Shape | Tall bottle or flask with a narrow mouth | Cup shape with a wide mouth |
| Lid | Screw-on, often with a pour spout or cup | Press-on or slide lid, often with a straw |
| Leaks | Usually leak-proof when sealed | Usually spill-resistant, not leak-proof |
| Temperature | Longest hold, thanks to the sealed lid | Hours, though a sip opening lets some heat out |
| Drinking | Pour or unscrew first | Sip anytime, one-handed |
| Best for | Soup, all-day coffee, hikes, job sites | Commutes, desks, the gym, everyday hydration |
Thermos for the long haul. Tumbler for the daily grind.
Which one should you choose?
Choose a thermos if your drink needs to stay hot until dinner, you're packing soup for lunch or it's going in a bag, a toolbox or a tent.
Choose a tumbler if you want something to sip from all day, you drive a lot and need it to fit a cupholder, or you like plenty of ice and a straw.
Lots of people end up owning both, and that's not a bad plan. Wondering whether a tumbler will survive your bag? Read are drink tumblers leak-proof?
Quick answers
Is a tumbler the same as a thermos?
No. Both can be vacuum insulated, but a thermos is a sealed flask and a tumbler is a lidded cup made for sipping.
Which keeps coffee hot longer?
Usually a thermos, because its sealed screw-on lid lets out less heat than a tumbler's sip opening.
Can you put hot drinks in a tumbler?
Yes, if it's an insulated stainless tumbler. Just be careful sipping right after you pour.
Is a thermos leak-proof?
Most are when the lid is fully screwed on, which is why they're a better pick for bags.
Branded drinkware that gets used
Want tumblers engraved with your logo?
Tell us the colors, the quantity and your logo. Our 20 oz and 30 oz tumblers include a 3″ laser engraving.
