GstarCAD provides two calculators, one is quick calculator, a calculating dialog box similar to the one in Windows system, as shown in the following picture, To open it, press CTRL + 8

CAL command

Another kind of calculator we can use is through command: enter CAL, and press Enter key, then we are prompted to enter the Express, as shown in the following picture,

For example, we can enter 3000/18, then press Enter key, we will get the calculating result, as shown in the following picture,

Sometimes, we may need to calculate in the middle of drawing, for example, when we are prompted to specify the second point after specifying the first point to draw a line, we can simply enter a single quote before entering CAL command without disrupting the drawing process, as shown in the following picture,