Your best plan is to use a logarithmic scale, so that it starts at 1. The next division (say, at 1cm) represents 10, the next 100, then 1000, up to 10^25, so each division is the next power of 10. 1 could represent the radius of the H atom. On this scale the Earth-Moon distance would be about 19. Cairo-Alexandria is about 15.6. Earth's diameter is about 17.4. 1 light-year would be off-scale about 26.2. 21.5 is about the radius of Earth's orbit. 10.5 would be the height of a human being and 6.4 the diameter of a human egg cell. 2.5 to 3.5 the length of a virus, and 3.7 for bacteria. The estimated size of the universe would be around 37.2. The subdivisions of the main divisions: 0.1 to 0.9: 1.26, 1.58, 2, 2.51, 3.16, 3.98, 5.01, 6.31, 7.94 multiplied by the previous power of 10. So 10.5 is about 31,600,000,000 times the radius of the H atom.