Height of Mountains

I'm thinking of having a a samll range of mountains on my SIM. What is highest you can take a mountain too on a SIM on SL?
Is it 150m? Can you go pass that limit by chance. If so what kind of Estate tools setting whould i have

By sim I assume you mean mainland, right?

Island owners can completely terraform their land, but estate owners of mainland can only change the height of terrain within a limited range of about 4m.

I'm not sure if that restriction applies to someone who owns the entire sim, however. Best way to find out is give it a try. Right-click on the land and select Edit Terrain. Try raising a mountain range on a selected portion of land, then Revert if it doesn't work.

On the mainland, it depends what specific sim you're talking about. Some are terraformable; some are not. Of the ones that are, there's a range. Some, like Indigo where I live, are modifiable to +/- 40M. Others are +/- 20M. Still others, like the ones Regan mentioned are just +/- 4M.

The general rule of thumb is that older regions are more flexible than newer ones. For some reason the Lindens saw fit to narrow the range as they added more and more land. Knowing what's old and what's new requires that you've been here a while, and that you have a good memory, but in any case, when you buy land, you should find out about the terraforming range before you make the purchase.

On islands, the sky is literally the limit. You can set any part of the land from zero altitude (ocean floor) to 768 meters (max height of "normal" space in SL).

In general, you can not make mountains "to scale" in SL, any more than you can make a mountain to scale in your local City Park in RL. Individual sims are way too small to realisticly model mountains, and the building constraints in SL won't allow you to make more than foothills, anyway.

Most mainland sims are limited to +/- 4M terraformability. Even if you own the whole sim, the Linden's won't change that on Mainland properties. Even if you did manage to locate a large Mainland parcel with +/- 100 M terraform limits, you wouldn't have enough surface area for the base of a mountain.

To have wider control, you need a private sim. They typically are set to +/- 100 Meters trerraformability. Bear in mind that even if you own the entire sim, that sim is only a square of land 256 Meters on a side. Compared to the footprint of a real mountain, that is barely big enough to make a bump.

Also, the terrain mesh is a 0.5M grid. That means that two adjacent points on the grid are 0.5M apart side to side, regardless of how much they differ vertically. The grid is too coarse to scale down a mountain peak successfully.

If you max out the Estate Manager setting for terraform limits, you might manage to get a spike of land up to 768 meters. But it would look terrible, with such steep sides and with the terrain texture very badly distorted on the steeper slopes. A real mountain, however, is thousands of meters high at the peak, and thousands of meters wide at the base...

In my experience, having done whole-sim terraforms and having made a sim with a small "mountain" in the middle of the sim, you generally want a peak no more than 60 to 70 Meters high, if you want something that "looks right" in-world. Anything more than that, and the terrain mesh gets too distorted, and the surfaces start looking really bad.

There are some tall mountains on the mainland...not that it addresses the question of how to build your own, but if you want to see what one looks like, there's a nice one in Rogna(? can't get in to check right now) that I used to visit when I had land in Larsen.