What population do you need to get high density residential/commercial in SimCity4

Buildings in simcity 4 are grouped into and develop in stages. Each stage defines an increase in the capacity of a tile, its population density. These stages unlock at set numbers of population.

High density buildings are of stage 7 or higher. The tallest buildings in the game (the growable skyscrapers) are all stage 8. Therefore, the following table entries mark their introduction for the various categories:

Note: The thresholds are in total residential population. That means you don't need 25952 high-wealth residents to get your first high-wealth high-density building, just 25952 total residents.

+----------+--------------+-------------+
| Category | High density | Skyscrapers |
+----------+--------------+-------------+
| R§       |         6647 |        9571 |
| R§§      |        25952 |       43859 |
| R§§§     |        25952 |       43859 |
| CS§      |         4616 |        9571 |
| CS§§     |        15356 |       43859 |
| CS§§§    |        15356 |       43859 |
| CO§§     |        25952 |       43859 |
| CO§§§    |        25952 |       43859 |
+----------+--------------+-------------+

These figures are regional populations of the listed type.

You need to have that many people in your city belonging to the specific category before skyscrapers will be built. This may be a reason why you see so many figures touted: people think it depends on your total population, but it depends on each specific "type" of sim.

Note that in order to grow these buildings, you need a high density zone, water access, high desirability for the type of zone you want to build, enough demand that the building actually gets built*, and time. The game will only build a certain percentage of zoned tiles as high density (1% of a specific wealth and type at the listed numbers) so you initially can only support very few skyscrapers. The number goes up to 49% high density, 20% skyscrapers for residential.

*A building will only get built if there's enough 'demand' to fully fill that building. Say a R§§ skyscraper holds 4000 sims. Then it will only be built if your 'demand bar' for R§§ is above 4,000. Note that demand can't go over 6,000 without mods, so some custom buildings with higher capacities than that require mods before they can be built by the game.

As the previously linked wiki page has been lost to time and space, I will reproduce the full info there below:

The stage caps are defined in percentages. The game will try to build buildings as per the percentages in the tables below. So if your city has between 518 and 622 inhabitants, all R§, and 100 zoned 'lots', then it will try to have 45 stage 1 lots, 40 stage 2 lots, and 15 stage 3 lots.

If there isn't any way to build a higher-stage lot, but there's a lower stage lot available that fills an available zoned stage, the game may build this instead. This could happen by for example zoning a lot of low-density residential (some people like housing their sims in suburbs). As there are no low-density lots of stage 5 and greater, the game will build lower stages instead.

A trick I often use that's based in this is building alternated 1x1 medium and large density lots. The biggest buildings in them are stage 5, the different types of townhouses. The game can't merge the lots as they are of different densities. This allows you to have growable European style city centres (which often don't have too many high-rises in them) with densely packed rows of townhouses.

Note: If you do not have the Rush hour expansion, use the second column, even for the §-class residents. (The developer changed R§ in the expansion to prefer tenements more over duplexes).

+--------+----------+-------+------+------+------+------+------+------+------+
| Pop R§ | R§§/R§§§ |  S1   |  S2  |  S3  |  S4  |  S5  |  S6  |  S7  |  S8  |
+--------+----------+-------+------+------+------+------+------+------+------+
|      0 |        0 | 100 % |      |      |      |      |      |      |      |
|    300 |      300 | 95 %  | 5 %  |      |      |      |      |      |      |
|    360 |      390 | 80 %  | 20 % |      |      |      |      |      |      |
|    432 |      507 | 60 %  | 35 % | 5 %  |      |      |      |      |      |
|    518 |      659 | 45 %  | 40 % | 15 % |      |      |      |      |      |
|    622 |      857 | 30 %  | 45 % | 25 % |      |      |      |      |      |
|    746 |     1114 | 27 %  | 40 % | 28 % | 5 %  |      |      |      |      |
|    895 |     1448 | 24 %  | 36 % | 30 % | 10 % |      |      |      |      |
|   1074 |     1882 | 21 %  | 33 % | 32 % | 14 % |      |      |      |      |
|   1289 |     2447 | 17 %  | 30 % | 35 % | 18 % |      |      |      |      |
|   1547 |     3181 | 14 %  | 26 % | 33 % | 23 % | 4 %  |      |      |      |
|   1856 |     4135 | 12 %  | 23 % | 31 % | 27 % | 7 %  |      |      |      |
|   2227 |     5376 | 10 %  | 20 % | 28 % | 32 % | 10 % |      |      |      |
|   2672 |     6989 | 9 %   | 17 % | 25 % | 36 % | 13 % |      |      |      |
|   3206 |     9086 | 8 %   | 15 % | 21 % | 39 % | 14 % | 3 %  |      |      |
|   3847 |    11812 | 7 %   | 13 % | 18 % | 37 % | 19 % | 6 %  |      |      |
|   4616 |    15356 | 6 %   | 11 % | 15 % | 34 % | 24 % | 10 % |      |      |
|   5539 |    19963 | 5 %   | 9 %  | 12 % | 32 % | 27 % | 15 % |      |      |
|   6647 |    25952 | 4 %   | 8 %  | 10 % | 28 % | 30 % | 18 % | 2 %  |      |
|   7976 |    33738 | 3 %   | 7 %  | 8 %  | 26 % | 27 % | 24 % | 5 %  |      |
|   9571 |    43859 | 2 %   | 5 %  | 7 %  | 22 % | 24 % | 27 % | 11 % | 2 %  |
|  11485 |    57017 | 2 %   | 4 %  | 6 %  | 19 % | 22 % | 25 % | 16 % | 6 %  |
|  13782 |    74122 | 1 %   | 3 %  | 5 %  | 16 % | 19 % | 24 % | 21 % | 11 % |
|  16538 |    96359 | 1 %   | 2 %  | 5 %  | 13 % | 17 % | 21 % | 25 % | 16 % |
|  19846 |   125267 | 1 %   | 2 %  | 5 %  | 10 % | 15 % | 18 % | 29 % | 20 % |
+--------+----------+-------+------+------+------+------+------+------+------+

For commercial, all types use the total regional commercial capacity, so add up the total amount of each type you have. Commercial offices follow the same table, using the R§§/R§§§ column. Commercial services use different percentages:

+---------+----------+-------+------+------+-----+-----+-----+-----+-----+
| Pop CS§ | CS§§/§§§ |  S1   |  S2  |  S3  | S4  | S5  | S6  | S7  | S8  |
+---------+----------+-------+------+------+-----+-----+-----+-----+-----+
|       0 |        0 | 100 % |      |      |     |     |     |     |     |
|     300 |      300 | 95 %  | 5 %  |      |     |     |     |     |     |
|     360 |      390 | 92 %  | 8 %  |      |     |     |     |     |     |
|     432 |      507 | 89 %  | 10 % | 1 %  |     |     |     |     |     |
|     518 |      659 | 86 %  | 12 % | 2 %  |     |     |     |     |     |
|     622 |      857 | 83 %  | 14 % | 3 %  |     |     |     |     |     |
|     746 |     1114 | 80 %  | 16 % | 3 %  | 1 % |     |     |     |     |
|     895 |     1448 | 77 %  | 17 % | 4 %  | 2 % |     |     |     |     |
|    1074 |     1882 | 74 %  | 18 % | 4 %  | 3 % | 1 % |     |     |     |
|    1289 |     2447 | 71 %  | 19 % | 5 %  | 3 % | 2 % |     |     |     |
|    1547 |     3181 | 68 %  | 20 % | 5 %  | 4 % | 3 % |     |     |     |
|    1856 |     4135 | 66 %  | 20 % | 6 %  | 4 % | 4 % |     |     |     |
|    2227 |     5376 | 64 %  | 20 % | 6 %  | 5 % | 4 % | 1 % |     |     |
|    2672 |     6989 | 62 %  | 19 % | 7 %  | 5 % | 5 % | 2 % |     |     |
|    3206 |     9086 | 60 %  | 19 % | 7 %  | 6 % | 5 % | 3 % |     |     |
|    3847 |    11812 | 58 %  | 18 % | 8 %  | 6 % | 6 % | 4 % |     |     |
|    4616 |    15356 | 56 %  | 18 % | 8 %  | 7 % | 6 % | 4 % | 1 % |     |
|    5539 |    19963 | 54 %  | 17 % | 8 %  | 7 % | 7 % | 5 % | 2 % |     |
|    6647 |    25952 | 52 %  | 16 % | 9 %  | 8 % | 7 % | 5 % | 3 % |     |
|    7976 |    33738 | 50 %  | 16 % | 9 %  | 8 % | 7 % | 6 % | 4 % |     |
|    9571 |    43859 | 48 %  | 17 % | 9 %  | 8 % | 7 % | 6 % | 4 % | 1 % |
|   11485 |    57017 | 46 %  | 14 % | 10 % | 9 % | 8 % | 6 % | 5 % | 2 % |
|   13782 |    74122 | 44 %  | 14 % | 10 % | 9 % | 8 % | 7 % | 5 % | 3 % |
|   16538 |    96359 | 42 %  | 14 % | 10 % | 9 % | 8 % | 7 % | 6 % | 4 % |
|   19846 |   125267 | 40 %  | 15 % | 10 % | 9 % | 8 % | 7 % | 6 % | 5 % |
+---------+----------+-------+------+------+-----+-----+-----+-----+-----+

Finally, industry has fewer growth stages, and uses this table:

+-------+---------+-------+------+------+
|  ID   | IR/M/HT |  S1   |  S2  |  S3  |
+-------+---------+-------+------+------+
|     0 |       0 | 100 % |      |      |
|   300 |     300 | 99 %  | 1 %  |      |
|   360 |     390 | 98 %  | 2 %  |      |
|   432 |     507 | 97 %  | 3 %  |      |
|   518 |     659 | 96 %  | 4 %  |      |
|   622 |     857 | 94 %  | 6 %  |      |
|   746 |    1114 | 91 %  | 9 %  |      |
|   895 |    1448 | 89 %  | 11 % |      |
|  1074 |    1882 | 86 %  | 14 % |      |
|  1289 |    2447 | 83 %  | 16 % | 1 %  |
|  1547 |    3181 | 79 %  | 19 % | 2 %  |
|  1856 |    4135 | 75 %  | 21 % | 4 %  |
|  2227 |    5376 | 71 %  | 22 % | 7 %  |
|  2672 |    6989 | 66 %  | 23 % | 11 % |
|  3206 |    9086 | 61 %  | 24 % | 15 % |
|  3847 |   11812 | 56 %  | 25 % | 19 % |
|  4616 |   15356 | 50 %  | 26 % | 24 % |
|  5539 |   19963 | 44 %  | 27 % | 29 % |
|  6647 |   25952 | 37 %  | 29 % | 34 % |
|  7976 |   33738 | 31 %  | 29 % | 40 % |
|  9571 |   43859 | 23 %  | 32 % | 45 % |
| 11485 |   57017 | 16 %  | 33 % | 51 % |
| 13782 |   74122 | 8 %   | 35 % | 57 % |
| 16538 |   96359 | 7 %   | 29 % | 64 % |
| 19846 |  125267 | 7 %   | 23 % | 70 % |
+-------+---------+-------+------+------+