Fermi Questions (fermiquestions.org) is a Wordle-like game where you try to guess the answer to Fermi estimation questions with 6 or less tries. After each guess, you'll see if your answer was too high or too low. You win if your guess is within ±20% of the correct answer.
Example questions:
- How many new cars were sold in the US in 2024?
- How many humans have ever lived (including those currently alive)?
- How many chickens are slaughtered for meat every year?
The skill of Fermi estimation is also extremely useful if you want to perform better here on Manifold. As Philip Tetlock shows in his book Superforecasting, many of the best forecasters break down complex questions into smaller, more manageable components which is exactly what you can practice when playing the game.
In the first 24 hours after going live it had some 1,100 unique visitors, which primarily came from Hacker News. Resolution source is the unique visitors count on the publicly available analytics dashboard: https://plausible.io/fermiquestions.org
Update 2025-08-04 (PST) (AI summary of creator comment): In addition to the default bot-filtering by the Plausible analytics tool, the creator reserves the right to manually exclude any suspicious activity from the final unique visitor count.
Update 2025-08-04 (PST) (AI summary of creator comment): A unique visitor is defined as a distinct visitor to the website within a 24-hour period, based on their IP address. A user who visits on different days will be counted as a new unique visitor for each day.
1,000People are also trading
I've greatly appreciated people here sharing screenshots of their game statistics; please continue to do so! This is great fun!
Another clarification that might be important: For the purpose of this market a unique visitor is defined as a distinct visitor to the website within a 24-hour period, based on their IP address. So if the same user returns on a different day, they are counted by the analytics dashboard as a new unique visitor.
One of the main downsides of the game so far was the focus on doing somewhat trivial binary search if one did not succeed in getting within ±20% of the correct answer with the first guess.
I think found a solution to bring the focus a bit away from the binary search and prompt people to rethink the original question once more, but now in light of new information. I would greatly appreciate feedback from all of you.
The game now shows a hint after the second incorrect guess. For example the hint "The US covers 1.87% of the Earth's surface." is displayed for the question about what percentage of the Earth's surface is land.
I hope that this brings into the game a whole new dimension where you have a second moment after the initial Fermi estimation to really think through your guess and the assumptions you have made. How does the new information received through the hint impact your model?
I think those things put together now make the game a very compelling training ground for getting better at Fermi estimation and updating your beliefs in light of new information without over or under-reacting.
Idea I just thought of:
Global/regional leaderboards of running average number of guesses needed and/or running average log closeness of first guess to correct answer (maybe subtracted the standard error so that you also need to have achieved it over many games), to trigger competitiveness in players
@TheAllMemeingEye I like the idea, but I just don't know if a leaderboard can work on something as easy to cheat at as this
I love how my guess distribution looks approximately normal.
I want to take a crack at the game difficulty:
I imagine the intended way to play this is to do a fermi estimation to get within an order of magnitude of answer, then change my guess up or down an order of magnitude based on the higher/lower hint. A correctly done Fermi estimation should put your two guesses as red above and below the true answer in the worst case, and you can guess the lower number * 3.2 to guarantee a win if both are red. If your first guess is yellow, you can win in the next guess, and if your second guess is yellow, you can win on the next turn. Therefore the fair expectation for someone talented at the game to consistently be at or below would be 3 guesses.
I think it is fair to give people one additional guess to account for mistakes , but each guess you give someone past the third pretty much expands the target they have to hit with their initial estimation by an order of magnitude in each direction from the correct guess. I recommend 4 guesses, but if you think my viewpoint is very different from the average person who would play this, I wouldn't complain about 5.
Another idea:
Your questions are all very "global" in that someone from anywhere in the world would have a good chance at knowing enough to estimate the answer. This is a good thing, but it could limit your options. What if there were more specific question (think piano tuners in Chicago) that came with a few pieces of information (Chicago is a city in the midwestern US and is the 3rd most populous city in the US, in the piano tuner example) to allow people from anywhere to have a shot at answering them?
Love it. Others have said a similar thing, but it seems like a shame that it feels like 95% of the game is coming up with the first guess, followed by trivial (but tbh still quite satisfying) binary search.
I think one challenge is that users might be quite bimodal between people who know how to do Fermi estimation (for whom the first guess is where the fun is) and people who don't (who might spend a few guesses just to get the order of magnitude and then might run out of guesses for the final precision).
Suggestion: all users keep going until they reach 6 guesses and then get scored based on how close they are to the final answer. Two downsides: you need more precise source numbers, which might be frustrating if top uses feel the source has false precision, and it makes it less wordle-esque
But ultimately, I think the there's a tension between "wordle-esque and satisfying for mass users" and "really good Fermi estimation game that is satisfying to fans of Fermi estimation". It might be that your current middle road is already optimal!
@Fion The idea of always playing 6 rounds and being scored on proximity is so smart! Kind of reminds me of Geoguessr.
@Fion Thank you for sharing your thoughts here. I'm not sure about your suggestion, I'll have to think about this in more detail, but I greatly appreciate it. For the time being, I think I did find a solution to bring the focus a bit away from the binary search.
Namely, by showing a hint after the second incorrect guess. For example the hint "The US covers 1.87% of the Earth's surface." is displayed for the question about what percentage of the Earth's surface is land.
This now brings into the game a whole new dimension where you have a second moment after the initial Fermi estimation to really think through your guess and the assumptions you have made. I also really like how this actually trains one to get better at updating your beliefs in light of new information. What do you think? Is this addressing some of your concerns?
@Fion It should be live now, though I guess if you have played all questions already you can only try it out with the new question for today which is about how many students are currently enrolled in medical school in the US.
@MingCat Yeah. For example:
This is the current one. I’m not going to share it to my wordle like groups because it’s a bit cringe. The best wordle clones have an air of mystery to them.
Fermi Question of the Day: 6 August 2025
"How many students are currently enrolled in medical school in the US?"
I won using 1 out of 6 guesses. Can you beat me?
🟢
I’d revise it to be more like:
FermiQ 6/8/25
"How many students are currently enrolled in medical school in the US?"
🟢
@OP I’m also not happy with the share text and I’ll change it today. I’d say maybe more like this:
Fermi Question of the Day: "How many students are currently enrolled in medical school in the US?"
I got the right answer using 1 guess.
🟢
Or is this still a bit cringe?
@danftz still a bit too wordy imo. I personally hate any pre-generated text that uses first person language. It sounds inauthentic.
You should look at some other Wordlelikes for inspiration. They’re minimalistic to a fault. Here are some examples:
Strands #521
“Paint me a picture”
🔵🔵🔵🔵
🟡🔵🔵
#travle #965 +5
🟧🟧✅✅🟧🟧🟩🟧✅
Zip #141 | 0:16 🏁
With 1 backtrack 🛑
#waffle1293 5/5
🟩🟩🟩🟩🟩
🟩⭐🟩⭐🟩
🟩🟩⭐🟩🟩
🟩⭐🟩⭐🟩
🟩🟩🟩🟩🟩
🔥 streak: 870
🦾 #waffletitan
Thanks for all this feedback! I think the current version is now a lot better:
Fermi Question of the Day: "How many students are currently enrolled in medical school in the US?"
⬇️✅
@danftz better but still some cruft.
The “Fermi Question of the Day” text is unnecessary. The “fermi question” part is in the URL, and we can see it’s a question from the text.
The URL is a little long. It doesn’t need the https or the day marker
It’s nice to have a date or puzzle number to differentiate. Just something like short date, or a number.
Consider giving it a funky shorthand name. “Fermi question” isn’t SEO friendly, and probably costs a fair bit URL-wise. “FermiQ” could work? Fermiqle? Not essential to do, though.
@OP Thanks for those additional recommendations! I greatly appreciate it, but I guess a few things you mentioned have some trade offs:
The URL in the share text does unfortunately need the https, because otherwise it is not clickable on a number of platforms like Discord. But on X and other places it automatically removes the https for all links, so this is quite convenient.
The day marker is needed in the URL because otherwise you might get to a different question if a day has gone by and there is a new question of the day.
Where you are right is that the “Fermi Question of the Day” text can be removed, I’ll probably do that. Of course, a funky shorthand name would be quite great. I’ve spent quite some time on that a few days ago, but really struggled with finding something great. I bought the domain fermi.quest, but that seemed not that great either on reflection. Not sure I’m convinced by FermiQ, but I do really appreciate you bringing forward those name ideas.