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Lunch is not just a meal, it’s the point in the day around which all other activities revolve. Promo lunch bags prove that you respect the importance of lunch – but which one works best?

Since it’s summer, we’re focusing on lunch bags that keep lunch cold, as opposed to keeping hot food hot, which is a problem for future us. If you want to gift lunch bags that will bring joy in the form of a still-chilled can of pop at lunchtime, you may want to read this post. Or at least scroll down and read the results.

How Lunch Bags Work

Your lunch has two best friends in the fight to stay chilled: ice packs and insulation.

A photo of three lunch bags stacked in a pyramid, with an orange one on top of yellow and blue ones. All have YOUR DESIGN HERE printed in black on the front.

  1. 1 Ice Packs

    According to the second law of thermodynamics (check us out), heat moves spontaneously from a hot area to a cold area until both areas are equal temperatures. So when you put an ice pack and your lunch in a cooler, the ice pack absorbs the heat of the air and the heat of your lunch, cooling down both.

    This happens until everything in the lunch bag is the same temperature – so the air and the food will cool down while the ice pack warms up.

  2. 2 Insulation

    Once your ice pack has created that chilled environment, the lunch bag’s role is insulation: Keeping that cold in and any more heat out. Most do this using an insulation layer that’s sandwiched between an outer and inner layer. It’s usually made of some kind of closed-cell foam, which has a densely packed structure that prevents air and moisture from getting out or in.

    You’ll also notice that a lot of lunch bags are lined inside with shiny metallic foil. The part that’s doing all the work is the side you can’t see, facing out towards the hot air. That side is also shiny, and that shininess reflects the heat before it can reach your lunch. If you’re trying to keep your food warm, the foil on the inside reflects the heat in your food back at it, while the foil on the outside reflects cold air trying to seep in.

Method

To find out which of our coolers would stay the coolest, we ran two tests with slightly different approaches.

Test 1

  • We packed each bag with two cans of pop and two ice packs.

  • We added a thermometer probe inside the bag and fastened it.

  • We recorded the temperature every 30 minutes for three hours.

Test 2

  • We filled each bag as much as we could, adding one ice pack for every can.

  • We added a thermometer probe inside the bag and fastened it.

  • We recorded the temperature every 30 minutes for three hours.

We felt that Test 1 was more realistic – most people probably throw a couple of cool packs into the cooler and call it done. But it also put the bigger coolers at an unfair disadvantage, since it left them with more empty space to cool than the smaller coolers. So we did Test 2 to see how our results would change if all our coolers were stuffed as full as possible with ice packs and cans.

In both tests, we made sure to close and fasten the lunch bag lids, to allow for maximum insulation. We used a thermometer with a wire and had the screen outside the bag, so we wouldn’t have to open the bags and let in warm air. And we made sure the thermometer probe wasn’t touching any cans or ice packs, which would throw off the temperature readings.

Flipbooks

Test 1

Test 2

Key Takeaways

An illustration showing a clock set to 3 o’clock.

Our Lunch Bags All Got Colder Over 3 Hours

All of our lunch bags proved to be effective insulators. In both tests, the temperatures inside all our lunch bags decreased over 3 hours. How much the temperature dropped varied, and in most cases, Test 2 saw higher percentage changes. In Test 2, the median percentage decrease was 16.18%, compared to 12.16% in Test 1.

The Neoprene and Metal Containers Kept Their Cool

Two of our containers didn’t use a foam insulation layer. Our retro lunch box is made of metal, which is a bad insulator and should therefore not make for a very effective lunch box. It looks cool, though. And our neoprene bag is made of the same open-cell foam as wetsuits and koozies, which uses little air bubbles to prevent heat traveling through the foam via conduction. (We’ve also done a koozie test!)

Remarkably, both of these performed the best of all our lunch bags in both tests. The metal lunch box dropped by a frankly astounding average of 25.3% across both tests, while the neoprene bag did even better, with an average drop of 26.5%. This probably comes down to the fact that they’re two of the smallest containers, but it’s still impressive.

A photo of a retro tin lunch box with an orange and turquoise watercolor on the front under the words YOUR DESIGN HERE. Below it is a photo navy blue neoprene lunch bag with grey edges and YOUR DESIGN HERE in white on the front.
A composite photo showing two round ice packs with YOUR DESIGN HERE on the front, and a black and blue cooler-style lunch box with YOUR DESIGN HERE on the front.

Pack in As Much Ice As You Can

Quick refresher: In Test 1, all of our lunch bags got two cans and two ice packs. In Test 2, our lunch bags were stuffed with as many ice packs as we could fit while trying to maintain a 1:1 ice pack-to-can ratio.

The mean percentage decrease for all the lunch bags in Test 1 was 12.74%, compared to 16.39% for Test 2. In other words, on average, the lunch bags in Test 2 got colder than the lunch bags in Test 1. So you can say that in general, more ice packs leads to a colder lunch bag.

This is partly because more ice packs means more heat absorption, and partly because more ice packs means less space for warm air – a chilling combination. However, even the two ice packs alone were still very effective at cooling the lunch bags.

Smaller Is Mightier

Size does matter when it comes to lunch bags: The smaller, the better. Less space means less hot air for the ice packs to absorb, plus a smaller surface area for heat transfer. It’s similar to why it’s easier to cool down a smaller room than a bigger room.

If you need a big cooler, it’s worth stocking up on ice packs. As we expected, although our three biggest coolers were effective in both tests, they did significantly better when they were crammed with ice packs and soda in Test 2 than when they only had two of each in Test 1.

A composite photo showing a quilted light blue lunch bag and a purple lunch bag with a flap lid, both printed with YOUR DESIGN HERE on the front.
A photo of a grey and black cooler-style lunch box with the IGLOO logo on the front.

The largest cooler, the Igloo® Yukon Box Cooler (Q93251), dropped by 9.59% in Test 1 and 16.42% in Test 2.

A photo of a black cooler box with the RTIC logo on the lid and a bottle opener clipped to the front.

The RTIC Everyday Cooler (Q96321) decreased 12.16% in Test 1 and 15.94% in Test 2.

A photo of a red and grey cooler-style lunch box with carry in style printed on the front and a black net side pocket.

The KOOZIE® Expandable Lunch Cooler Bag (Q64668) dropped by 10.96% in Test 1 and 13.04% in Test 2.

It’s also no coincidence that two of our smallest containers – the retro lunch tin and the neoprene bag – were our top performers. Even without any fancy insulation layers, these two managed to stay the coldest simply because they didn’t have as much air to cool down in the first place.

Your Lunch Bag Buying Guide


Only got 30 minutes?
Here’s your lowdown on what to buy based on your budget and taste.

A photo of a white and black cooler-style lunch box with YOUR DESIGN HERE in blue on the front.

You’re on a Budget

Q34306 Non-Woven Cooler Bag

The Non-Woven Cooler Bag held its own against more expensive options in both of our tests. In Test 2 it was the only lunch bag in the top five that cost less than $5. And in Test 1, it had the lowest price in the top six (it came sixth.)

A photo of a turquoise neoprene lunch bag with grey edging and a zipper, and YOUR DESIGN HERE printed in white on the front.

You Like a Bag

Q59332 Klutch Neoprene Lunch Bag

If your preferred lunch receptacle is “brown paper bag gone high tech,” the best performer in this style is the Klutch Neoprene Lunch Bag. Made from the same material used for koozies and wetsuits, this bag has handles and a zipper, so it’s a bag rather than a boxy cooler. It was the top performer in Test 1, dropping a whopping 27.63% over 3 hours, and second in Test 2, even though it still decreased in temperature by 25.4% in that test.

A photo of a blue cooler with a black handle and zipper, and YOUR DESIGN HERE in white on the front.

You Like a Cooler

Q20377 6-Pack Insulated Bag

The 6-Pack Insulated Bag is an insulated nylon box shaped like a classic cooler, with a long adjustable handle and a useful front pocket. It has enough room for a satisfying lunch (or a six-pack.) It was consistently chilly in our tests, coming seventh in Test 1 and fourth in Test 2, dropping an average of 16.32%.

A photo of a blue and black cooler with a black handle and top zipper and YOUR DESIGN HERE in white on the front.

You’re Very Hungry or Thirsty

Q93251 Igloo® Yukon Box Cooler

Small is cool but sometimes you need a bigger bag to accommodate your snacking needs. The cooler that best combines size with cooling efficiency is the Igloo® Yukon Box Cooler. It’s got an approximate volume of 722in³, compared to, say, the Q34306 Non-Woven Cooler Bag’s compact 286in³. Despite being so much bigger, the Igloo® still dropped an average of 13% across both tests, even making the top 10 in Test 2.

The Bottom Line

When you’re choosing the coolest lunch bag to give away, think small – and consider throwing in some customized cold packs. We’ve learned that fancy insulation is optional, but ice packs are essential.



Q# PRODUCT NAME IMAGE + VIDEO AVERAGE TEMPERATURE CHANGE AVERAGE PERCENTAGE CHANGE VIEW PRODUCT
Q1393 KOOZIE® Six-Pack Cooler
A photo of a turquoise lunch cooler with a black handle and YOUR DESIGN HERE printed in white.
-12F -16.93% View Product
Q20377 6-Pack Insulated Bag
A photo of a navy blue lunch cooler with a black handle and YOUR DESIGN HERE printed in white.
-11F -16.32% View Product
Q22816 Budget Lunch Bag
A photo of a light blue lunch bag with a short black and blue handle, and YOUR DESIGN HERE printed in white on the front.
-10.5F -14.35% View Product
Q22817 Budget Kooler Bag
A photo of a lime green lunch cooler with a black handle, a black zipper, and YOUR DESIGN HERE printed in black on the front.
-10.5F -14.86% View Product
Q23522 Non-Woven Lunch Bag
A photo of a blue lunch bag with a flap closure, a black handle, black trims, and YOUR DESIGN HERE in white on the front.
-8.5F -12.05% View Product
Q34306 Non-Woven Cooler Bag
A photo of a dark green lunch cooler with a black handle and YOUR DESIGN HERE printed in white on the front.
-12F -16.99% View Product
Q35241 Retro Lunch Box
A photo of a retro metal lunch box with a blue handle and a clip closure. It has an orange and turquoise splash design on the front, under the words YOUR DESIGN HERE in blue.
-16.5F -25.25% View Product
Q59332 Klutch Neoprene Lunch Bag
A photo of a turquoise neoprene lunch bag with a grey trim and YOUR DESIGN HERE in black on the front.
-18.5F -26.51% View Product
Q64159 Non-Woven Thrifty Lunch Kooler Bag
A photo of a black and purple lunch bag with a short purple and black handle, and YOUR DESIGN HERE in white on the front.
-10.5F -14.82% View Product
Q64668 KOOZIE® Expandable Lunch Cooler Bag
A photo of a red and grey lunch cooler, with a black zipper and black handle.
-8.5F -12.00% View Product
Q65181 Non-Woven Wave Design Kooler Lunch Bag
A photo of a boxy orange lunch bag with YOUR DESIGN HERE on the front in black.
-10F -14.01% View Product
Q68570 Bellevue Insulated Lunch Tote
A photo of a burgundy lunch bag with the Genomix Research Center logo on the front, a black tab, and black click closures at the top.
-6.5F -9.13% View Product
Q71346 Velcro Closure Insulated Lunch Bag
A photo of a bright orange lunch bag with a short black and orange handle, and YOUR DESIGN HERE printed on the front in white.
-6.5F -9.18% View Product
Q71354 Traveler Insulated Lunch Bag
A photo of a bright blue lunch cooler with a black net side pocket and black zipper, and YOUR DESIGN HERE printed in white.
-9.5F -13.98% View Product
Q71362 Tucson Aluminum Foil Insulated Lunch Bag
A photo of a dark green lunch cooler with a black front, black netting and black handle, and YOUR DESIGN HERE printed in silver on the front.
-11F -15.35% View Product
Q71367 Zipper Insulated Lunch Tote Bag
A photo of a light blue cooler bag with YOUR DESIGN HERE printed in black on the front.
-4.5F -6.28% View Product
Q93251 Igloo® Yukon Box Cooler
A photo of a grey cooler bag with black handles and the Igloo logo on the front.
-9F -13.00%
Q96321 RTIC® Everyday Cooler
A photo of a black cooler with RTIC in grey on the front.
-10F -14.05% View Product
Q96518 Arctic Zone® Repreve® Lunch Cooler
A photo of a grey lunch bag with a black zipper and black handle, and a tab with the Arctic Zone logo on the front.
-8F -11.57% View Product

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Natasha Lavender

Natasha is an experienced writer and editor who has covered topics including technology, health and safety, business, and pop culture. Her work has been published by Good Housekeeping magazine, Forbes, Success, and more.

View all posts by Natasha Lavender