Free Model Railroad Scale Tools Scale Conversion Calculator Convert real (prototype) size to scale size, or convert scale size to real size. Scale To Scale Converter Convert inches to metrics, and convert the size of model railroad scales to other scale sizes (e.g. convert HO scale to OO gauge, or N scale) Track Grade Calculator Work out the track grade based on the length of track run and the vertical rise. Helix Design Calculator Work out helix dimensions to design and construct a working model railroad helix. Scale Speed Calculator Measure scale speeds for trains to cover the distance from point A to point B.