Polar Instruments Si8000m and Si9000e are widely used in industry to calculate transmission line parameters. Beyond just the usual w, h, and t parameters, Polar will account for etch profile and soldermask overlay effects, for example, to calculate characteristic impedance more accurately than a tool that only considers rectangular geometries and one dielectric layer.
If you aren't able to buy a license for it yourself, but you are using a full-service board fab, your fab may be able to use it to generate trace geometries for you, if you give them your stackup.
Even if you don't use Polar, if you specify impedance control in your fab notes, your board shop is likely to use it (or a similar tool) to adjust your design to achieve the impedance you specified.
For quick and dirty calculations, I have recently been using CGI-Wcalc. Results tend to be within a few per cent of Polar, which is often good enough for the board shop to be able to adjust things to achieve a very good impedance match.
As the comments have said, if your concern is that a 1.9-mm-wide trace is taking up too much real estate, the best solution is probably to use a multilayer board so that you can have a dielectric height on the order of .25 mm (or even thinner if your design requires really high density), and a trace width less than 0.5 mm.