A data-backed approach to buying sandwiches

Which Pret A Manger sandwich offers the best value for money?

For those who don’t know, Pret A Manger is a British sandwich chain with a faux French name. It is a ubiquitous feature of working life in London with its slightly communist red star adorning streets from Westminster to Canary Wharf. But it is strictly a capitalist concern that is owned by a German conglomerate based in Luxembourg. It is affordable in a London way and—because some of its sandwiches have green stuff in them and because it does salads—is ostensibly a healthy choice.

Using my nascent Python skills for web scraping and visualisation, I’ve outlined six different options for sandwich buying at Pret based on different conceptions of value.

The dataset has 37 sandwiches with nutrition data from Pret’s website and take-away pricing collected from five Pret stores in Westminster in April 2022. We managed to visit all the stores in less than 30 minutes thanks to the density of Prets around Victoria Station, where our office was temporarily based, and around Westminster more generally. It’s good to know that after a hard day’s work at Downing Street or a straining session in Parliament the country’s leaders can source an affordable snack.

The data is explained in more detail at the end of this piece and is available on GitHub if you’d like to use it. Let’s see what it says about sandwich selection.

1. Shop above the line

Perhaps you already have some favourites at Pret but you want to shop in a more value-conscious way? Or perhaps you don’t like to have your entire sandwich buying strategy dictated to you by a strange article on the internet?

Either way, you can decide whether energy or protein is more important to you and then choose options from above the regression line in the graphs below. The further above the line an option is, the better value it is on the relevant metric (protein or energy) at that specific price point. For example, if you’re shopping for protein, the Chicken Caesar Bacon Baguette is a better buy than the similarly priced (and also similarly chickeny) Naked Katsu Chicken Baguette.

2. Protein for money

Protein is expensive, so how can you get the most for your pounds in sandwich form? In a Ham and Cheese sandwich where £1 will buy you 10.5g of protein.

Here are the top 10 sandwiches ranked on grams of protein per pound. Honourable vegetarian mentions to the Brie, Tomato and Basil Baguette and the Free-Range Egg Mayo.

3. Energy for money

Perhaps you don’t care about protein—crucial building block of life be damned—and instead you’re just really hungry. How can you get the most energy for your money in a sandwich?

In a shock double win, it’s the Ham and Cheese sandwich again. £1 gets you a surprising 177Kcal with the total sandwich clocking in at an impressive 530Kcal.

The top 10 below features several vegetarian options, likely ranking high on the energy front thanks to their cheese or humous content. The Free-Range Egg Mayo just manages to scrape another top 10 finish.

4. Overall protein per sandwich

Perhaps money is no object to you and instead, you place value on having a single-serving meal with the maximum amount of protein? Well, then your best option is the Tuna Melt Toastie which has a ludicrous 37.7g of protein per serve. Can your body even absorb this much protein in one sitting? Science is unsure but an absolute beefcake like you won’t let that stop you.

Though the Ham and Cheese has dropped from medal position, it still ranks a respectable fourth and is a great value option. Unfortunately for the vegos, the Classic Cheese Toastie is the only vegetarian option that makes the top 10.

5. Overall energy per sandwich

Again, perhaps you value the convenience of a sandwich but this time just want to maximise the amount of energy in a single serving? The Swedish Meatball Hot Wrap is the answer. It packs a stonking 661Kcal—an average adult need only eat three to meet their daily energy quota. But ask yourself, are you an average adult?

Vegetarians rejoice; there are two solid options in the top three—Posh Cheddar and Pickle Baguette and the Falafel and Halloumi Hot Wrap. Go to them.

6. Play along The Protein-Energy Frontier

Perhaps you don’t want to maximise either protein or energy on a cost or total basis. This next chart could be for you—behold The Protein-Energy Frontier.

The chart just features sandwiches that have greater than 20g of protein, so all are reasonably good on both the total protein and energy front. Dot size indicates price. You can see our old friend the Ham and Cheese really punches above its weight in terms of cost.

Seeking to maximise both protein and energy, while still enjoying variety, one could choose to play along the frontier on the top right, perhaps one day enjoying a Posh Cheddar and Pickle Baguette and the next day a Ham, Cheese and Mustard Toastie.

Conclusion

I hope you enjoyed this data-backed guide to buying sandwiches. It was fun to collect the data and visualise it and I’ve learnt how to use Python libraries Beautiful Soup and Seaborn.

It has been pointed out to me that some eccentric types might choose sandwiches using criteria other than price, protein, and energy. That’s fine; those people can make their own guide.

A note on the data

The data (GitHub) was collected from Pret’s website and from five Pret stores in Westminster in April 2022 by me and Josh. The dataset includes 37 sandwiches for which we found prices. There were 13 sandwiches listed on the Pret website at the time that we could not find. These tended to be slightly more niche items like the Dukkah Spiced Squash and Feta Flatbread and the Vegan Eggless Mayo and Cress.

It turns out that Pret sells sandwiches at different prices at different stores. Financiers of Westminster take note; while you’ve been scouring the world for the increasingly few arbitrage opportunities that exist in the Internet age, one was hidden in your own backyard. We found three dramatically different priced sandwiches in Pret stores within half a kilometre of Victoria Station.

Not only was it shocking to find that Pret is playing us for fools but it also made collecting accurate data a challenge. To be conservative, I’ve used the highest available sandwich price we encounter in the wild.

Thanks to Hannah and Josh for reading earlier versions of this piece.