Water temperature mixing calculator

Short version: A friend and I made a simple tool for figuring out how much water of given temperatures to mix in order to reach a desired temperature:

It can be visited here: https://water-mix-temp.fly.dev

Technologies used:

• Python
• Uv
• HTMX
• Fly.io

Long version:

I recently became a dad for the second time, and we are relying on baby formula to feed the baby. When mixing formula with water, you need to mix it with sterile/boiled water. Ideally, you want the formula to end up around body temperature. A trick is to mix boiling water with previously boiled, room temperature water from a container. But the ratio needs to be right.

When we had our first child, I asked a good friend, who is a chemist, if he could help me figure out a way to calculate the mixing ratio, given the temperature of the available water amounts. He cooked up a Python script, and I used this a little bit before I ended up with a pretty good gut-feeling for the whole thing.

During some of the naps of the new baby, I coded up a quick web-app to have the calculator available on my phone at all times. Not really necessary, but something to do while the baby slept. This allowed me to try a few new things that had been on my to-do list for a while. Uv, an extremely fast Python package installer and resolver, written in Rust, and Fly.io, a cloud service for hosting apps leveraging microVMs. While only dipping my toes, both of these seem very promising, and have been added to my toolbox for future use.