# Capacity of a children's playground

For the story I'm writing, I have a scene that takes place on a playground. Because I suffer from enjoy World Building Disease, I wound up making an exact plan for the playground. Specifically, it is 40,000 ft² with some swings, spring riders, a couple 100 ft² sandboxes, several tunnels, a balance beam, quite a few balance "steps", a fairly substantial "obstacle course" (e.g. climbing boulders, jungle gyms), and a modest "fort" (i.e. platforms, steps, a slide).

Now, here is where I have a bit of a conundrum and world building question... This is supposed to serve 24 children.

Similar forts claim to have a capacity of 45 children (just for the fort?). While that particular claim seems ridiculous, even those more conservative estimates I've seen are much higher than my own estimate of 4-5, and I also have a lot more raw square footage. It seems as if my capacity estimate is way off...

... or is it? This world isn't populated by humans, but by anthropomorphic animals.

Why is this an appropriate, even necessary, amount of space for my world? ("Because it is not gratuitous overkill, even for humans" is an acceptable answer, if you can justify it, but this doesn't seem to be the case.)

(For bonus points, how does age factor into this? That is, does my ratio of equipment to open space need to change depending whether the children or younger or older?)

Note that the "24 children" target is simultaneous occupancy; that is, a full two dozen children all running around at the same time. They also cover all species; herbivores, omnivores, and carnivores all mixed together (with appropriate supervision, of course!). The dietary ratios are also somewhat skewed; no more than half are "pure herbivores" (i.e. vegetarian), about half eats some mix of meat and not-meat, and a few (2-4) are obligate carnivores. (The latter — e.g. felines — can and do also eat fruits and vegetables, but generally try to minimize grains, and most of their calories must be from meat.)

• Back of the envelope says that a 40k area is 200' per side; spaced evently, each kid gets their own grid square of 16' per side if spaced evenly.
– Tom
Jul 2 at 18:52
• 40,000 square feet is 3700 m². Divided by 24 children that is a whopping 154 m² per child. For reference, a basketball court is about 436 m²; I would say that the area of one basketball court for every 3 children is clrealy more than sufficient. Jul 2 at 18:59
• @Tom, right; 200'×200' is indeed the actual dimensions. I should note, however (may add this in an edit) that's the total area. For example, Dickinson City Part is maybe one sixth the size and looks just the equipment would be comfortable for maybe 12 people. Jul 2 at 19:15
• Ages matter. The activities and space requirements of 24 three-year-olds will be very different from 24 ten-year-olds. At my kids' school, 300 kids fill a playground half the size (about 20k sq ft) during lunchtime, with about 75 of the youngest supervised in one corner on the climbing and other classic activities. The 200-or-so older kids mill around the rest of the space under looses supervision, jockey for swings, and make up assorted games with about 20 assorted balls hurled into the seething mass. Jul 2 at 23:01
• Ok, but that's exactly and argument FOR making it smaller! I mean, your question is - "I want to have a playground this big, but it seems too huge. Please help me find a reason why it should be so ginormous.". So... why not simply put a smaller playground in your story? Problem solved. Why do you need to have it be big anyway? Jul 5 at 6:18

As the other answers have pointed out, 40,000 ft² is a much larger space than required for 24 human children.

However, as the question is asking for justification as for why this space is much more suited to these 24 anthropomorphic animal children, we just need to look at how normal human children and normal animal children compare.

The average mobile puppy can easily keep pace with the average human child in terms of speed, and outpace in terms of stamina. Now scale this up so both are human-size, and the puppy would now be able to outpace the human child by a long margin, and as such would require much more room for running about and expending energy than a similar-size human child, probably by a factor of ten or so.

As a real world example, my local village children's park is approximately 2,000ft², while the dog park less than half a mile away is in the region of maybe 12-15,000ft². Sure, it's designed to cover a larger catchment area, but the simple fact is young dogs need much more space to run around in than young humans.

The same goes for many (but not all - tortoises, anyone?) young animals.

For bonus points, for younger animal children, I'd imagine you would follow the same principles as for younger human children: less open space; smaller forts; everything much smaller and safer, with more focus on things which help balance, coordination, and group play.

Also somewhere for strong adult supervision positioning, maybe raised up above ground level? Or a perch, for Uncle Bulgaria the Vulture to keep his beady eye on the little reprobates.

For older children, more room to run and chase each other and get up speed, with jumping and climbing obstacles spotted around for agility and dexterity. Maybe a track around the outside, for the big cats?

As I say, you would adjust for age probably much the same as you would for human children.

For added bonus points, you should consider adding species-specific items of play, depending on the make-up of your children.

For example, as mentioned, a track around the outside, or a long straight section would be ideal for your running animals (big cats, horses), with jumps for the deer.

A climbing frame would be a requirement for monkeys (monkeybars!), lemurs, sloths, etc; perches and hoops for birds to fly through; a mudbath for the hippos..

You could have a bit of fun with the details, depending on the level of anthropomorphising(?) you wish to do to your children-animal hybrids.

• "more focus on things which help balance, coordination", definitely! "...group play", er... maybe for the herbivores, some of the others may be rather less social than humans 🙂. (That, actually, is the potential reason I had in mind, that some of them would simply want space; not necessarily to run around, but to be "alone".) I ended up downsizing dramatically, and now you have me reconsidering. Great answer! Jul 4 at 1:42
• FYI, no birds, only mammals. Thanks for reminding me of the extra importance of climbing equipment, though; I wasn't thinking of that! Fortunately, I am actually designing several spaces for different age groups (hence that part of the question) from youngest to oldest, so you haven't messed up the work I've already done too badly. Jul 4 at 1:49
• Sigh. It's not really on topic, but you're doing a number on my expectations of what equipment I "need" 🙂. For instance, I'd thought I could avoid more "advanced" climbing structures at least for the really young children, but apparently not. Even for humans. Jul 4 at 2:12
• @Matthew "maybe for the herbivores" Uh... have you never visited a dog park on a busy day? When you have a bunch of dogs together, especially young dogs, they will tend to form play groups. If you have 24 dogs you might have 3 or 4 groups, often blending and separating as the members get distracted, interested, tired, etc. Jul 5 at 0:25
• @Matthew Aduly predators are, sure. But we're talking about children. Adolescents of almost all mammalian predator species do the same thing dogs do... and those that don't are hardly going to be interested in your playground except as a place to hunt prey. I don't see intelligent animals suffering the existence of those sorts of antisocial predators. Jul 5 at 0:47

Current use is not what builders expected.

There is a playground about a mile from my house. When I discovered it I was surprised. It was brand new and wonderful and hardly being used. Around it were vacant lots and condemned houses. An enormous abandoned Sears distribution center loomed a block away.

The city put the playground in first. All of those lots and houses are gone now, and there are apartments. The distribution center has become a bunch of upscale shops, with apartments above them. The playground is now full of kids all the time.

Your playground was built with the expectation of higher occupancy than it currently has. Maybe it is new and the developers expect more kids in the future. Maybe it is old and there used to be more kids filling it up.

Either way, the excess space gives energy to the story. The expectation of more in the future or the memory of more in the past both give energy to a present where there is less.

• I'm upvoting this because it's a good answer, and yes, would make a good story. Unfortunately it doesn't work for my story, as in my case, 24 actually is the expected / designated occupancy. Jul 3 at 13:28

40,000 square feet for 24 children amounts to almost 1700 square feet of space per child - that's the footprint of a modestly sized house for each child! This should be plenty of space for activities that require wide open spaces, as well as stationary installations like slides and swings. This playground could easily handle a much larger capacity.

As a point of comparison, a professional basketball game has about 4x the density of adults, with 10 individuals in 4700 square feet (470 square feet per person). An American football game has a similar density to the proposed playground, with 22 adults (plus referees) on a 48,000 square foot field (2100 square feet per player). If you've ever watched an American football game, vast swaths of the field are completely empty most of the time - there is plenty of space.

Age could play a factor, in that less space would be required for smaller children. They don't run as fast or as far as older kids, and playground equipment sized for their age will be smaller than that for bigger kids.

• I'm not sure this answers the question. This would imply that, by humans standards, this is way too much space. (Ahem: "This playground could easily handle a much larger capacity.") So, "why might it be reasonable for anthropomorphic animals?" Jul 2 at 19:17
• That's straightforward - the playground has a higher capacity, but it is not always fully at capacity. The story event occurs at a time when 24 children were playing there. Jul 3 at 10:23
• @kaya3, well, sure, that's essentially Willk's answer. That's not stated in this answer, though. Jul 4 at 2:09

This playground should accommodate megafauna and possibly even dinosaurs

40,000 ft² is very large for 24 human children. It comes to 1,666 ft², which means that human children are not going to have much contact with each other. However, if we need to accommodate children of larger species, it all makes sense.

If you see the movie "Zootopia", there are different areas and establishments for different species. While smaller species have the right to come to larger species' places, those places are designed first and foremost to accommodate those larger species.

So, while 1,666 ft² is a lot for a human child, it's not that much for baby elephant, and for juvenile sauropod it begins to look too tight.

Now, how children of different species can play together without stepping on each other is a different question, which would likely be answered by allocating different time slots for differently sized children.

• Argh, my bad; I should have mentioned I'm not trying to take on the square-cube law. But because I didn't this is a viable answer. Incidentally, "how children of different species can play together without stepping on each other" makes me think of the "can't wait to be king" scene from the (original, darn it!) Lion King 🙂. Jul 2 at 19:30

The playground playacre1 you describe is large enough for 24 children, but just barely. It would help if you could make the sandboxes bigger. Allow me to explain --

A sandbox that's 100 square feet is basically 10' x 10'. Let's assume both sandboxes are identical, that each sandbox is surrounded by a wooden retaining wall that rises 1 foot from the ground, and also extends 1 foot below ground. That depth is maybe not typical in the real world, but deeper is obviously better because of more law2:

more volume == more sand == more sand


I assume that typical playground sand is just regular sand, and thus has an angle of repose of approximately 34°, so it seems reasonable that children could remain completely covered if they dig all the way to the bottom of the sandbox and lie perfectly flat. (Obviously on their backs, and with some kind of straw for breathing, like a snorkel.)

This will actually be made even easier if other children are at the bottom of the sandbox too, displacing more sand, which they would be. But neither sandbox can hold the 11 children necessary for an even split. I've tried a few different packing schemes on graph paper, but if all the kids are kind of uniformly biggish, and the sandbox is square, the most I can fit into one sandbox is seven.

If we assume 14 children can fit in the sandboxes, that still leaves nine unaccounted for.

"Several" tunnels means at least three. (And per Willk's Proviso, there are no take-backs with plurals.)

A boulder can do in a pinch (but is obviously not ideal), and you used the plural, so that's two.

I've never seen a playground with fewer than two spring riders, so that's two more hiding places (especially if any children have spring-like appendages, or plausibly look like spring riders themselves).

The fort is frankly too obvious, but there's always one dummy who goes for that stuff. (The tunnels are not dumb, because tunnels are dark and it takes a brave kid indeed to crawl into a dark place filled with creepy-crawlies and then sit silent and motionless as the local arthropods come a knocking.)

The balance beam is worthless unless it's large, and even then, the kid would need to levitate like a magician's assistant.

A jungle gym is an obvious trap: you can see right through the thing, and most kids learn at some point that it's safest to stay away from one rather than run the risk of getting caught trying to clamber out of it when poop meets fan.

So that only leaves the balance steps. If this is what you have in mind, we've still got one kid left.

You didn't mention any trees, bushes, or other substantial vegetation; any embankments, gullies or ravines, streams or other bodies of shallow water (and anyway, shallow water is translucent -- or if it's not, it's a lousy hiding place).

Is this a reasonable scale after all, even for humans?

We're so close, and I really want this to work, so I'm going to assert there's at least one tree with decent foliage, and at least one of the kids can climb it.

So there: 23 hiding places.

But the seeker is really going to have to project, or nobody will hear when the countdown ends. And each group of kids can really only play one or two games before they realize the possibilities have been exhausted.

1 1 acre = 43,560 sq ft

2 not to be confused with Moore's Law

• I almost feel like this is comically missing the point, but upvoting because it's hilarious 🤣. Jul 3 at 13:33
• Should not the more law enforcement with “more fun”?
– SRM
Jul 3 at 14:30
• Tom: tunnels in sand can be redug to change configuration. Boulder can be rolled. Jungle gym works as hiding spot once seeker is conditioned to skip checking. Thus the field is replayable.
– SRM
Jul 3 at 14:35
• @SRM Re: more law: you'd think so... ;)
– Tom
Jul 3 at 16:28

Rich People

The playground is funded by a rich person or several rich people to provide a fun place to interact for their children. Either that, or the playground is in a really rich part of the city.

As we all know, there are rich people who spent an atrocious amount of money on extravagance. Spending some money on a large playground for their children seems like one of the more reasonable uses of money.

It's in the Countrysides

There are rich farmers. Land in the countryside are cheap. Why not?

It's for a Luxury Resort/Amusement Park

Think Disney World, but for rich people.

Society is more advanced or productive

Maybe it's far in the future where people have a lot of land. Society now expects people to have a lot of space to work with. Free-ranged children develop better.

Animals Run Faster and Need Bigger Space to Play

We all know that cheetah cubs need lots of space. Free-ranged cubs are tastier develop better.

• Good answer! Won't work for my case (the entity with which the playground is associated isn't flush with cash), but a) I didn't specify that, and b) this is the sort of answer that's valuable for this site. Upvoted. Also, um... not sure what to think of your correction in the last sentence 😉. Jul 4 at 13:32

You're over-thinking it. Which is awesome.

Playgrounds serve a variety of purposes apart from simple entertainment. They are (nominally at least) safe areas for children to engage in physical exercise, imaginative play and (often mediated) social interactions. Learning to play with others, share limited playground equipment etc. is good for their social development after all.

What we don't tend to acknowledge is that playgrounds are places where children can be exposed to mild physical danger, where they can (and do) challenge themselves and others to do stupid things and end up with minor injuries - scrapes, bruises and so on. This teaches them to be confident, to accept minor hurts in the pursuit of sweet victory, to dominate their peers... uh... compete with their friends in a relatively safe environment.

In your case you have a mixture of different base types, perhaps with their own individual needs. The carnivores need high energy, burst activities - things they can chase, climb, slide down, bounce off, swing from, tumble in. Herbivores are more likely to need space to run, cooperative activities, some quieter spaces and a few activities devoted to strength rather than fast reactions. Omnis are just going to do whatever, because they're like that.

So you need space to chase each other around in, things to both climb and hide in, preferably in colors bright enough to cause retinal burns because what kid doesn't love radioactive green slide sets? It needs to be spread out enough to let them pack up, chase or be chased, because going without these developmental experiences will leave them emotionally stunted, socially inept, unable to deal with minor troubles.

Gee, just like ubiquitous connectivity did to the last couple of generations. Who knew?

And now we've arrived at the more serious part of the answer.

Because your society has a mixture of different animal types, it is critical that the children are raised to maximize the social stability between the groups. Not doing so will tend to damage society as a whole as the younger generations grow up as more insular, less able to handle interactions across the food boundary, more prone to distrusting or outright hating those that are different.

The founders of this society have studied the problem extensively, and social scientists have determined the minimum requirements for adolescent socialization. They've produced a set of guidelines that any shared play space must allow, and mandated that space be assigned for these play areas within the community based on population and other factors.

And it's these rules, formulated for the good of the society, that result in your playground being the size that it is. For other communities or areas with a different distribution of children the parks will be different. Your area has this size park because it's what the guidelines require.

I don't think it is outrageously oversized. That is only 200 feet per side, less than 100 yards.

The thing is, a playground doesn't have an importance to density. Twenty-four children running around and playing on a 200' by 200' space would be fine.

They don't have to use the whole thing. They won't have to spread out to their own isolated spaces of their proportion. They play together somewhere in that space. It does not have to be near capacity. So if 45 is the capacity, a few children might play there quite fine.

If space is not limited then I think it would be perfectly reasonable for them to have built a 200' by 200' playground, not really tailoring it to, "Only about 24 children would ever be using this."