Editing Metric system (section)

===Candela and Watt relationship===
Candela is about the luminous intensity of a moderately bright candle, or 1 candle power. A 60&nbsp;[[Watt]] tungsten-filament [[incandescent light bulb]] has a luminous intensity of about 800 lumens<ref>{{cite web|title=Lumens and the Lighting Facts Label|url=https://www.energy.gov/energysaver/save-electricity-and-fuel/lighting-choices-save-you-money/lumens-and-lighting-facts|access-date=11 June 2020|website=Energy.gov|language=en}}</ref> which is radiated equally in all directions (i.e. 4{{pi}} steradians), thus is equal to {{math|''I''<sub>v</sub> {{=}} {{sfrac|800 lm|4{{pi}} sr}} ≈ 64 cd}}.