CALCULATING METRIC QUANTITIES IN PLACK TERMS

The metric units based on the CIPM 1990 electrical standards have exact practical Planck equivalents--as do the meter and atomic clock second as a matter of course. Although such great accuracy is seldom needed—it is interesting that the conversions are exact rather than approximate.

atomic clock second = 371/20 trice

meter = 371/(20×0.299792458) centipace

volt₉₀ = (20/371)pi×0.4835979 [voltage unit]

ampere₉₀ = ½×(200/371)×0.4835979×2.5812807 [current unit]

coulomb₉₀ = ½×4.835979×2581.2807 quad

joule₉₀ = ½×(200/371)pi×4.835979²×25.812807 erg

newton₉₀ = ½×(200/371)²pi×4.835979²×2.5812807×0.299792458 dyne

kilogram₉₀ = ½×(200/371)pi×4.835979²×25.812807×0.299792458² ounce

In 1983 the metric authorities officially adopted the number 299792458 in the definition of the meter, then in 1990 the numbers 4835797 and 25812807 were adopted to define the electrical standards. These rather ungainly numbers are the metric system's and I'm not responsible for them. Since they are basic to metric standards and measurement proceedures, I merely use them (with the decimal point conveniently placed) to obtain conversion factors. I have no reason to expect that the metric custodians will decide to revise any of these three numbers any time soon but if they did it would not change the humanly-scaled Planck units. It would simply change the exact conversion factors which express the 1990 metric electrical standards in practical Planck terms.