This is not a simple calculator, it is designed for calculations when creating new missions for GTA 1. A very useful thing. Written in 1998 in VisualBasic, which is now almost never used.

Health setting:
The utility may not run if "MSVBVM50.DLL" is not present on your PC. This computer system file may not be on many modern PCs, but it just allows you to run utilities written in VisualBasic.
Just downloading msvbvm50.dll is not enough, you need to put it in one of the folders in the Windows directory. This is the System32 folder for a 32-bit copy of Windows, or the SysWOW64 directory for a 64-bit version. It is necessary not only to put the library in place, but also to register it in the registry. After that, the program will start without error.
Inside the archive there is a MSVBVM50.exe program that does all this work for you.

1. Unzip the contents.
2. Open MSVBVM50.exe and click on "ok", the program must be in the same folder as MSVBVM50.DLL so that it can see MSVBVM50.DLL and install it in the registry.
3. Open GTAcalc and use.