This is a preliminary review (more on what this means).

I became curious about sun exposure recently. I did an abbreviated review of some of the relevant literature and came away thinking that whether sun exposure is beneficial or not was unclear at that level of investigation (this seems to be an open question for most LWers as well).

One consensus that did seem to exist was that sunburn is bad and a thing to avoid. In order to be able to avoid it, and especially to be able to avoid it while still getting the potential benefits of non-burning sun exposure, I figured it would be helpful to know how long I could be in the sun without getting burnt.

This could be determined by trial and error, and maybe that would be a valid approach if I felt a good sample size could be obtained in an enjoyable, low-risk way. I don’t like sunburn though (and it probably wouldn’t be low-risk), so I was personally interested in finding a calculator that would predict this.

If you google something like “sunburn calculator” you’ll get a lot of results. But they are incredibly bad. Most seem highly untrustworthy, many clearly have bad inaccuracies, some don’t gather sufficient information for meaningful calculation, and ~none are transparent about their methodology or how to interpret their results.

So I’ve built a better, bad, sunburn calculator (view, copy).

It’s better than others because:

1. At least some of the results have high interpretability. It can calculate how many minutes it takes for 1% of people in this situation to develop a sunburn, and what percent of people in these conditions will get a sunburn after the indicated number of minutes.

2. There’s transparency. Sources are cited (in notes), calculations are available on-sheet (formulas & hidden rows), and I’ve added relevant notes and context where appropriate to help with interpretability.

3. Relatively feature-rich. It accounts for sunscreen protection typically not working as advertised, and includes some information about how much sun exposure to actually aim for.

4. Information quality is probably better. I didn’t spend much time vetting studies or calculations used, but I still strongly suspect that the information quality is significantly better than otherwise readily available. I think it probably mostly asks for the right inputs as well, given the state of knowledge today.

But despite being better, this calculator is still quite bad:

1. Information is only lightly vetted. As said in #4 above, the studies weren’t highly vetted and some certainly seemed to have issues but were still included when I couldn’t find something better quickly and easily. There may be better info out there, or existing info just may not be that great (I mainly lean toward the latter).

2. Most results are limited. You’ll see that a number of calculations will throw warnings in many circumstances. Most of the best info I found only pertained to a subset of conditions, without a clear way to apply them to other situations.

3. This UX isn’t the best. Maybe I’ll make a web or mobile app someday, but for now, you need to make your own copy of this sheet for use.

Still, I think it’s good to have a better version (I find myself using it often), even if it’s still what I would call bad.