We have re-designed and re-imagined one of our classic apps — the Cowculator. This handy tool will help you work out the concentration and nutritional content of your cappuccino. The new version includes two modes that can help you decide what size of cups to buy, and what size of baskets you should use, when you’re planning a new coffee setup. You can read the full instructions on how to use the app below — but first, indulge us as we tell a story that highlights how fragile our milk supply can be.

Have you ever noticed that sometimes an entire batch of milk simply refuses to froth? You check the date, and sure enough, the milk was freshly delivered that day, but it will not hold foam, no matter how hard you try. The culprit is usually lipolysis, the spontaneous breakdown of fats in the milk. This can happen for many reasons, including how the cow was fed as well as how the milk was treated.

But the Covid-19 lockdown exposed another, unusual reason for misbehaving milk. In Canada, the ‘buttergate’ scandal exposed a perfectly legal, but controversial practice: farmers had been feeding their cows palm oil (The Economist 2021).

When lockdown prevented Canadians from visiting their favourite cafes and bakeries, many turned to baking their own treats instead. Demand for butter skyrocketed, and farmers struggled to keep up. In Canada, high tariffs designed to protect the dairy industry prevent companies from importing milk, and laws regulating production capacity prevent farmers from adding more cows to their herds.

Unable to import or make more milk, farmers found another way to increase the butter supply: Feeding cows palm oil increases the proportion of butterfat in the milk — which means more cream, and more butter, from each litre of milk produced. The resulting butter has a higher palmitic acid content — a saturated fatty acid that makes the butter harder.

Feedlot cattle have replaced grass-fed cows throughout Europe and North America. These farms produce much more milk for a given amount of land, but the quality of milk is affected by the diet the cows are fed.

In 2015, Canadian butter typically contained 26% palmitic acid, but for butter on the market now, that figure is closer to 35% (Brehaut 2021). Eventually, bakers noticed that the butter was getting harder to work with, and some cafes started to complain about un-foamable milk.

How much of this change is really due to lockdown isn’t certain — but it does show how we can’t take milk for granted. Low prices mean that farmers are under pressure to produce more milk for less each year, while legislation designed to protect national industries can have unintended side-effects. Meanwhile, the dairy industry is under scrutiny for its environmental cost. The milk in your latte makes up by far the biggest part of the carbon footprint of your coffee, and a litre of cow’s milk takes more than a thousand litres of water to produce (Ercin et al 2011).

In that context, it’s more important than ever not to waste your milk. This app should help you to always use exactly the right amount for the drink you want to serve.

How to use the app

The app has three calculators built in: the original cowculator, a cup size calculator, and the ‘reverse cowculator’, which lets you start with the cup size and work out what size espresso you should be making. You can switch between calculators by clicking on the title at the top. 

Condensation and Aeration

Most of the terms in the app should be familiar to any barista, but these two might trip some people up. Condensation is the amount of water, from the steam, that condenses into the milk. The amount of water added ranges from 5-10%, depending on your machine — but if you don’t want to measure it, stick to the default value of 7.5%.

Aeration refers to the total increase in volume of the milk. This includes the foam, but also includes the extra water added by condensation — so the amount of aeration cannot be lower than the amount of condensation. We recommend aiming for an aeration level of 33%, but you can also adjust this figure if you like foamy cappuccinos or very flat flat whites.

The Cowculator

The original cowculator gives you the breakdown of coffee, fat, protein and sugar in your milk drinks. For a full discussion of these components, take a look at the OG cowculator blog post.

The Cup Size Calculator

This calculator is useful if you’re setting up a new cafe, or deciding what size cups to buy for your barista competition. If you start with a fixed espresso recipe, and input what strength you want your final milk drink to be, then the calculator can tell you what size cup you should use.

Put in the size of your espresso and the expected TDS, pick values for condensation and aeration (or stick to the defaults), and then decide how strong you want your drink to be. A typical cappuccino might be 1.4%, similar to a filter coffee. A flat white would often be stronger, perhaps around 2%. Click on ‘calculate’ and the app will give you an estimate of how much milk to put in your jug, and what size of cup you would need for that drink.

The Reverse Cowculator

The last calculator is for the rare occasion when you have a cup already, and need to pick an espresso recipe to work with it. This might help you if you’re deciding what filter baskets to buy, or how many shots you need to add to a Venti latte to be able to taste the coffee.

Put in the expected TDS of your espresso, and the target strength of your drink. Again, a cappuccino might be around 1.4%, while a flat white would often be closer to 2%. Enter values for condensation and aeration (or stick to the defaults), put in your cup size, and click ‘calculate’. The app will tell you how much espresso you would need to reach that strength in the cup, and you can design your espresso recipe accordingly.

For example, if I want to make a 6oz flat white at 2% strength, and my espresso is normally around 8% TDS, the app tells you that you need 36g of espresso. That suggests I should put away the 22g basket, and perhaps opt for an 18g dose instead.