Thanks for a calculator, it will be helpfull!
I have a good news for you :)
I modified LaserGRBL couple weeks ago for generating gCodes for Marlin. I posted the link on V1 forum, that mordiev mentioned in comment below. Here is the link to download: https://mega.nz/#!FslSUKIQ!PwdQzEIgfobTeFqY7bnPAJ4KTfN4al1FbNpqkKoL82s
Although it cannot be used as host, only as GCode generator.