/r/estimation

Photograph via snooOG

Ever wondered what the rate of gummi bear combustion needed to power a lawn mower is?

How fast do you need to throw a burrito to make it spontaneously ignite?

A subreddit dedicated to one of the most useful skills in life. Estimation.

This subreddit is dedicated to taking a stab at answering hypothetical, interesting and often untestable questions. In reality, you're never going to get a perfect answer. Some things just can't be tested. That's why estimation is such a valuable skill.


The following types of posts are allowed:

  • Links to reddit posts related to estimation. Please include the actual estimation in the post title. Example

  • Requests for estimations as long as they have the [Request] tag in the title. Self posts are preferred. Example

  • Links to websites related to estimation.


When fulfilling requests

  • List all assumptions made

  • Link to sources wherever possible

  • Use SI units for your final answer

  • Don't downvote because someone's answer is different. As long as they have made appropriate assumptions and done their calculations correctly, their answer is valid.


Reference dimensions

  • Wolfram Alpha (Mobile version doesn't have ads)

  • Length of an everyday car: 4.4 m

  • Weight of an everyday car: 1300 kg

  • Length of a football field: 100 m

  • Volume of an Olympic swimming pool: 2,500 m3

  • Muzzle velocity of a round fired from a 9 mm Glock 17: 375 m/s or 1,350 km/h


Estimation strategies:


Other related subreddits:

/r/estimation

14,728 Subscribers

0

Scaled PDF app for Android

I've given up on bluebeam ever making an app for Android phones.

Can anyone recommend an app that I can use, not only to mark up PDFs, but where I can set a scale and make measurements?

Bonus points for snapping to vector lines especially with an spen, and the ability to make/import my own mark up tools.

0 Comments
2024/05/30
00:49 UTC

4

If the US suddenly split in half from the furthest ends(horizontally obviously), how long would it take for the ocean water to meet in the middle?

Just a shower thought.

4 Comments
2024/05/27
02:47 UTC

5

What is the statistical likelihood of a single non-IVF pregnancy resulting in two sets of identical twins?

Asking as I know a family that had this happen and nobody has ever been able to articulate the numbers on how rare this is.

6 Comments
2024/05/24
02:22 UTC

0

How much is my brushless dc motor worth?

I have a brushless dc motor which has output power of 735W, voltage of 310 VDC and speed of 2500 r/min. How much do you think I can sell it for (second hand)?

1 Comment
2024/05/22
19:27 UTC

0

How much PSI would be required to launch a hook with a weight of 0.92 kg 100 ft in the air. (Building a grapple gun)

10 Comments
2024/05/18
13:32 UTC

1

Which US presidential candidate has more supporters that can dunk a basketball?

Standard NBA hoop and ball. If 2024 were to come down to a dunk contest, who has a bigger roster to pick from and what is the headcount for each side?

7 Comments
2024/05/02
04:27 UTC

0

How much would my reddit account cost?

2 Comments
2024/04/23
08:38 UTC

0

How much do you think my Reddit account is worth?

Hypothetically, if I were to sell it, I'm just wondering how much it would fetch.

5 Comments
2024/04/16
04:42 UTC

6

How long can the average human run nonstop before dying?

Supposedly, we can survive without food for a few weeks, we can survive without water for a few days, and without oxygen for a few minutes.

But how long do you all think someone would last jogging without stopping? To be more specific, here are a few parameters:

-average adult male

-initial 8 minute-mile pace

-can slightly lose speed over time (or not, if that makes estimation easier)

-no food or water during run

Personally my estimate would be a few hours, probably 3.

I'm sure it is much higher if the person has some running experience. What does everyone think?

14 Comments
2024/04/15
04:31 UTC

2

Mini (à la Niven) Ringworld

What would the radius be to have 1 gee centrifugal with a rotation rate of 1 (sidereal) day?
Been musing having a ring structure around the earth which could be a foundation to construct solar power stations which can be left aimed at ground stations and have sucessions of geostationary communication, ground and weather monitoring installed.
But not swift with the math needed to calculate distance or know if this can be acheived with current material engineering for building an "Endless Suspension Bridge" around the Earth.

1 Comment
2024/04/14
21:55 UTC

0

What percentage of people in the 2024 Total Solar Eclipse path of totality had no idea what was happening?

1 Comment
2024/04/08
20:08 UTC

2

How much carbon is in a metric ton of co2?

So let's say you are able to get a ton of pure co2, and extract the pure carbon from that. Would it just be a third of the weight, or something different? I googled it, and I couldn't find anything about the weight of carbon within co2, other than it being 1 atom's worth.

7 Comments
2024/04/07
03:33 UTC

0

What is the correlation between having had braces and having went to college in the adult population?

I'm betting it's impressive. Maybe you could do a time series as well adjusted to the growth in popularity of orthodontics in general.

It would be neat to see it start out at nearly 100% of all braces-havers are also college-goers, and fall as dental care becomes more widespread.

0 Comments
2024/04/06
02:22 UTC

6

What proportion of beds have people had sex in

What percentage of mattresses have been slept slept on. I’m thinking most hotel beds and most adults’ mattresses especially since some are second hand. But then maybe some people actually do get a new one every 7 years and nobody’s shagging in their childhood bed? Maybe they are?

8 Comments
2024/04/04
16:44 UTC

0

How much is my Reddit account worth?

I would never sell it, it's my baby.

8 Comments
2024/03/31
14:28 UTC

0

How many calories do you keep after vomiting?

Let's say you had 500 calories in 30 minutes. If you vomit immediately afterwards, how many calories do you retain? After 1 hour? After X hours?

Personal Note: I am pregnant. I would never throw up on purpose. I wish I wouldn't throw up right now.

7 Comments
2024/03/25
15:51 UTC

3

How much would it cost to start my own university?

Let's say I want to start a university, which in some time would be able to rival the Ivy Leagues? I would probably want to build it in the USA or Pakistan or Saudi Arabia... How much would it cost?

And let's say I start an online high school first in Pakistan (my country). How much would it cost to get started and get it to a national and international level?

2 Comments
2024/03/20
12:05 UTC

13

Are there more people simultaneously at sea or in the air?

3 Comments
2024/03/16
21:05 UTC

0

i want to start new school in india

iwant to start new privet school in india what is the detailed estimation for starting a new school

0 Comments
2024/03/16
05:46 UTC

4

If you were to select four random humans on Earth and construct a tetrahedron with those humans as vertices, what would be the average volume of that tetrahedron?

Assume that every living human has an equal chance of being selected. Express the answer as a fraction of Earth's volume.

I'm able to solve this question using datasets and a computer program. But estimating it using back-of-the-envelope calculations is proving to be a tricky task.

1 Comment
2024/02/26
20:53 UTC

0

Zero Air Gap Electric Motors could be improved?

Hello, I've been looking into online scientific articles and I was able to find a few ones about the subject. On these articles it is normally observed that the torque value of the motors doubles or even quadruples with the direct contact of the rotor and the stator while consuming the same amount of energy.

Some articles:

https://www.mdpi.com/1996-1073/13/17/4286

https://www.researchgate.net/publication/322650195\_Airgap-less\_Electric\_Motors\_with\_External\_Rotor

https://ieeexplore.ieee.org/document/8002357

However, I really can't find anything but a few articles, so I'd like to ask around and see if someone can help or give an educated guess.

For example, I was thinking of making the rotor rotate just like a hypocycloidal drive. On top of that, I was also thinking on making the stator and rotor into gear-teeth.

http://visforvoltage.org/sites/default/files/u6181/Animation%20Cycloidal%20Motor%2048%20-%2049.gif

This is a gif that I found here: https://visforvoltage.org/comment/77084

But I'm not qualified enough to even guess how this would improve the performance of the electric motor, nor I feel confident on even attempting on designing such thing.

What are your thoughts on the subject?

1 Comment
2024/02/23
22:58 UTC

Back To Top