Electrical Unit Converter

SI electrical base units

The International System defines a small set of electrical quantities that this converter is built around. The ampere (A) is the SI base unit for electric current, fixed since 2018 by the exact value of the elementary charge. The volt (V) measures electric potential difference, the ohm (Ω) measures resistance, the farad (F) measures capacitance, and the henry (H) measures inductance.¹ Together these five dimensions cover the quantities you reach for most often when designing or debugging a circuit.

Charge is measured in coulombs (C), which is derived from the ampere: one coulomb equals one ampere flowing for one second. The defining relations C = A·s, V = W/A, and Ω = V/A connect the electrical dimensions so that any unit can be expressed in terms of mass, length, time, and current, which is why a single current value can drive conversions across all of them.¹

Practical scale ranges in electronics

Real components operate far below the base-unit scale. Capacitors in RF circuits typically run from 1 pF to a few hundred pF; decoupling caps are 100 nF to 10 μF; bulk storage runs from hundreds of μF into the mF range.² Copper resistivity is about 16.8 nΩ·m at room temperature, while silicon can range from roughly 0.1 Ω·m to 2.3 kΩ·m depending on purity.³⁴

Recognizing typical scales for each component type

Inductors in electronics are commonly specified in nH, μH, and mH depending on the circuit.⁵ Knowing these typical ranges helps catch unit errors early, because a wrong prefix almost always points to a scale mismatch rather than a math error. If you calculate an inductance for a 100 MHz filter and get a result in henries rather than nanohenries, something has gone wrong before the conversion step, so pausing to compare the result against the expected order of magnitude is a fast way to sanity-check your work in the middle of a design review.

Resistance vs. resistivity — the material/geometry split

Resistance is a property of a particular component, and its value depends on both the material and the physical dimensions of that piece. Resistivity, by contrast, is an intrinsic property of the material alone and stays the same no matter how you shape it. The two are linked by the relationship R = ρ × L / A, which is why a longer conductor ends up with higher resistance while a thicker one ends up with lower resistance, yet the resistivity of copper holds at about 16.8 nΩ·m at room temperature regardless of the wire gauge you are holding.³

From resistivity to resistance through geometry

This distinction matters whenever you are selecting wire gauges, sizing PCB trace widths, or comparing interconnect materials for a design. You can look up the resistivity of any conductor and then calculate the resistance of any geometry directly from first principles, which is the standard approach for power budget calculations, voltage drop estimates, and trace thermal analysis. Because resistivity stays fixed for a given material while resistance scales with length and cross-section, the same formula lets you predict how a trace or cable will behave before you ever measure it on a bench.

Conductance and conductivity — reciprocal relationships

Conductance (G, siemens) is the reciprocal of resistance, so G = 1/R. Conductivity (σ, S/m) is the reciprocal of resistivity, meaning σ = 1/ρ, and the same geometric link applies through G = σ × A / L. When you place resistances in parallel, their conductances simply add together, which makes conductance the natural quantity for parallel circuit analysis and for the admittance calculations common in RF work.⁶

A round-number example shows the reciprocal at work. A 100 Ω resistor converts to a conductance of G = 1/100 = 0.01 S, or 10 mS in the converter's milli-prefixed output. Doubling the resistance to 200 Ω halves the conductance to 5 mS, which is exactly the inverse relationship the formula above predicts: enter either value into the Resistance or Conductance dimension above and the converter confirms the other side of the pair instantly.

Where conductivity shows up outside the lab

Conductivity appears in materials science, electrochemistry, and soil testing, often at values that look nothing like a metal conductor. Deionized water sits at about 5.5×10⁻⁶ S/m, drinking water ranges from 0.0005 to 0.05 S/m, seawater lands around 4.5 to 5.5 S/m, and annealed copper reaches roughly 58 MS/m.⁷ These reference points are useful because they let you sanity-check a measurement: if a supposedly pure water sample reads closer to seawater than to the deionized benchmark, contamination or a probe error is the likely culprit.

That enormous span, from microsiemens per metre for dilute solutions up to megasiemens per metre for metal conductors, is exactly why the converter covers both ends of the scale. Working across materials without switching tools keeps comparative tasks, like ranking insulators against conductors or tracking how a solution changes with concentration, inside a single view.

SI prefixes and the practical electrical scale

The SI prefix system maps electrical units across many orders of magnitude, and choosing the right prefix for a given domain keeps numbers readable. For this converter, common prefixes run from pico (10⁻¹²) to mega (10⁶). Picofarads cover RF bypass capacitors. Microfarads handle decoupling and bulk storage. Milliampere-hours rate battery capacity. Megavolts describe high-voltage transmission lines and lightning discharge. Knowing which prefix belongs to which domain is as useful as knowing the conversion factor itself, because it lets you spot-check results against the expected scale before committing to a design decision.⁸

A result in the wrong order of magnitude is the most common sign of a unit error. A PCB trace resistance lands in milliohms. When a conversion result surprises you, check the input prefix first, because a factor-of-1000 prefix mistake is far more common than an error in the underlying conversion math, and it takes seconds to identify once you know the expected range for the component type you are working with. Consequently, treating the expected scale as a sanity check is standard practice in hardware design, not just cautious habit.⁸