@AEGIS

here, i made an accurate one
<size=100%><pos=0%>Mach: {IAS/343;#0.00}
you dont need to do all of that extra math, the game accounts for altitude on its own to give you your IAS, all you have to do is divide the IAS by 343m/s to give you mach, it has been tested

@AEGIS The code should acount for altitude as well. Mach changes depending on altitude. So even though your going 2000mph, depending on your altitude, you might still be going Mach 9.

@AEGIS Hmm. I'll test it out, and try to fix the issue.

@TheFlightGuySP I have a problem, the label says that I'm going mach 9 even though I'm going 2000mph (Mach 9 is 6005mph)

@AEGIS Here is some modified code from the Wasp: <size=100%><pos=0%>Mach: {TAS/(340-clamp((Altitude*0.003937),0,43));#0.00}
You can modify the pos value to move the text left or right.
I tried making my own indicator, but it wouldn't work properly. It seems to be that the input listed below only works for gauges.

@TheFlightGuySP cool, do you know how exactly I could make a label one (I'm a noob in FT)

I got bored so I built one

@AEGIS There is a generic gauge, but it doesn't have numbers, just tick marks, so I'm not so sure about that.
On a label, absolutely!

@TheFlightGuySP thank you so much man, is there any way to make it go up to mach 10? Or if not on a guage, maybe on a label?

Ok, after some quick testing, it seems to be that, assuming that the steps below are followed, the input multiplier should be set to 180.
This seems to give the most accurate results.

Let me test this.

Perhaps. You would need a suitable gauge face (most likely the RPM gauge, since it's numbered 1 through 6). You would need to set the gauge zero to about -110, and set the input to (TAS*0.44704)/761. The 761 is the speed of sound in miles per hour at sea level static conditions. The rest of the math is for unit conversion (m/s to mph)

I have not actually tested this in flight (only in the designer), but I'm assuming it will work.