kVA to VA - Magnitude Slider

The metric system was born in revolutionary France. On 7 April 1795 the National Convention passed the law "sur les poids et mesures" - establishing the metre and the gramme. The original 1795 prefixes were Greek-derived: kilo (1000), hecto (100), deca (10) on the large side, and Latin-derived deci (0.1), centi (0.01), milli (0.001) on the small side. The kilo prefix has therefore meant exactly 1000 for 231 years as of 2026.

For 165 years the metric system survived on those six prefixes. Then in 1960 the 11th General Conference on Weights and Measures (CGPM) in Paris adopted the formal Systeme International d'Unites (SI). The 1960 reform added six new prefixes: micro (1e-6), nano (1e-9), pico (1e-12) on the small side, mega (1e6), giga (1e9), tera (1e12) on the large side. The slider in this widget reaches GVA - the giga decade added in 1960.

Two more decades on the small side were added in 1962-1964: femto (1e-15) and atto (1e-18). These came from need in nuclear physics for cross-section units (the barn is 1e-28 m^2). The large side got peta (1e15) and exa (1e18) in 1975 at the 15th CGPM. Zetta (1e21) and yotta (1e24) followed in 1991 at the 19th CGPM, prompted by digital storage capacity growth. As of 2024 the world's total grid capacity sits around 8 TVA (8e12 VA), nowhere near the zetta range.

The most recent additions were ronna (1e27), quetta (1e30) on the large side and ronto (1e-27), quecto (1e-30) on the small side. The CGPM adopted these in November 2022 at the 27th conference, motivated entirely by anticipated data-storage growth and the need for unique element symbols (R for ronna, Q for quetta) since the old yotta/yocto would otherwise have been overloaded.

The VA unit specifically dates to the 1880s. James Clerk Maxwell's "A Treatise on Electricity and Magnetism" (1873) introduced the foundational AC theory but not the VA terminology. The volt-ampere as a unit name appeared in German-language papers by Werner von Siemens around 1885, then in English in the AIEE Transactions of 1893 alongside Steinmetz's complex-power formalism. By 1900 VA, kVA and MVA were standard nameplate units on transformers and generators worldwide.

Modern transformer ratings span 10 decades. The smallest is the Tamura PB-2310 used in toy electronics at 0.5 VA. The largest is the Itaipu Dam shell-form transformer at 1700 MVA = 1.7 GVA. The slider in this widget covers the central 9 decades that matter for electrical engineering: VA, kVA, MVA, GVA. Beyond GVA we enter continental-grid-aggregate territory where MW (energy delivery) and not VA (apparent power) is the natural unit.

Software impact: the SI prefix system is the basis of computer storage prefixes (KB, MB, GB, TB, PB), although there is an ambiguity - sometimes these mean 1000 and sometimes 1024 multipliers. In 1998 the IEC introduced binary prefixes (KiB, MiB, GiB) that mean exactly 1024, leaving the SI prefixes for the 1000-multiplier meaning. The electrical-engineering kVA always means exactly 1000 VA - no ambiguity. The widget's brick-stack visualization correctly shows 1000 (not 1024) small bricks per large unit.