Voltage Calculator
Voltage as the per-charge promise: V = P/I from your load, the joule-per-coulomb reading made live down to a single electron, and the series-cell stack summed.
Voltage Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Load operating point only — no internal resistance
- DC reading; AC mains add rms conventions
In short: A 1,200 W kettle drawing 10 A runs on V = P/I = 1,200 / 10 = 120.000000 V. The promise card reads the same number as energy: every coulomb rounding the circuit is promised 120 J, and every single electron carries 1.923e-17 J of that promise — voltage is a per-charge commitment, not a pile of anything. Ten 1.5 V cells in series stack to 15.000000 V because pushes add. The page refuses to divide by no current: a circuit drawing nothing yields no voltage answer, only a wire that is switched off.
Formula
V = P / I · V = W/Q — joules per coulomb · cells in series add · 1 e = 1.602176634×10⁻¹⁹ C (exact)
Voltage is the energy promised per unit of charge: one volt means one joule for every coulomb that rounds the circuit. Power and current give it by division; the electron card scales the promise down to a single carrier using the exact elementary charge. Series cells stack because each coulomb is promised a wage by every cell it passes through.
Worked Example
- Enter the load's power and its measured current.
- Read the voltage and the per-charge promise on the same card row.
- Use the series card when stacking cells — pushes add, plain arithmetic.
- For the IR reading of the same number, the Ohm's law page holds the triangle.
Defaults: 120.000000 V; 120 J per coulomb, 1.923e-17 J per electron; ten cells stack to 15.000000 V.
Strengths & Limits Of This Model
Where this engine is strong
- Per-electron promise computed from exact e
- Series stack card for battery packs
Where it stops
- No source impedance or sag
- No AC rms or power factor
Practical Use Cases
Mains work
which rail a load expects
Battery packs
cell counts from series stacks
Teaching
the energy-per-charge reading, live
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Voltage Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is voltage, physically?
Energy per charge — the number of joules promised to each coulomb that completes the circuit. The page refuses the water-pipeline shorthand as an explanation but keeps the arithmetic honest: 120 V means 120 J per coulomb, and the card scales that promise down to one electron using the exact elementary charge.
Why does the page refuse I = 0?
Because V = P/I with no current is a division by nothing — and physically, a circuit drawing no power tells you nothing about its expected supply. Measure the draw with the load alive, or read the rating plate; a switched-off wire has no answer worth printing.
Why do series cells add but parallel cells don't?
Each cell promises its wage to every coulomb passing THROUGH it; in series a coulomb passes through all of them and collects every promise (10 × 1.5 V = 15 V). In parallel the coulomb passes through one cell — the voltage stays 1.5 V and the CAPACITY adds instead.
Is higher voltage always more power?
Only with a load that takes it: P = V·I, so voltage is half the product. The same kettle on a 230 V rail would draw about 5.217391 A for its 1,200 W — the load sets the trade, the rail sets the price per coulomb.
What does the electron card really show?
How small the per-charge promise is per carrier: 1.923e-17 J per electron against 120 J per coulomb, because one coulomb is about 6.24×10¹⁸ electrons. The physics is identical; only the bookkeeping scale changes — which is why engineers keep coulombs and chemists count electrons.
Why is negative power refused?
A negative power would be a source masquerading as a load — generators and batteries discharging have their own pages of physics (back-EMF, internal resistance). This page prices loads that consume, and refuses to blur the two.
How does this differ from the Ohm's law page?
Same triangle, different door: that page asks what voltage a current needs through a resistance; this page asks what supply a power-and-current load expects, and reads V as energy per charge. The cards are deliberately different questions — paired tools should not be mirrors.
Where does the volt come from, officially?
From the exact definitions: the elementary charge is fixed (1.602176634×10⁻¹⁹ C) and the joule and coulomb anchor the rest, so the volt is W/C all the way down. The page's per-electron figure is exact arithmetic on exact constants plus your measured load.