Your result
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Enter your values, then click Calculate result.How this calculator helps
Solve ideal DC voltage, current, resistance and power from two known values, or show a representable four-band resistor color code. Choose voltage and current, voltage and resistance, or current and resistance. The first and second fields follow that selection, so their units must be understood before entry. Voltage uses volts, current amperes and resistance ohms. Convert milliamperes to amperes by dividing by one thousand. A number copied from a component label can refer to a rating instead of an actual operating measurement; ratings and measured values should not be combined as if they describe one circuit condition.
How to use it
- 1
Choose voltage/current, voltage/resistance, current/resistance, or resistance-to-color-code mode.
- 2
Enter the named values in volts, amperes and ohms. In color-code mode choose the component tolerance band.
- 3
Click Calculate result to submit the inputs. Editing fields keeps the last submitted output until you click again.
- 4
Check the worked example, units and method limits before using the result.
Formula and methodology
V = I × R; I = V/R; R = V/I; P = V × I. Four-band nominal resistance = first two digit values × multiplier, followed by the selected tolerance band. Power modes: DC P = VI; single-phase real AC P = Vrms × Irms × PF; balanced three-phase P = √3 × line-to-line Vrms × line Irms × PF.
The calculator applies the disclosed heuristic to values entered on this device. It does not load private admissions data or claim to reproduce an institution's review process.
Worked calculation example
12 V across a load carrying 0.5 A implies 24 Ω and 6 W. A 100 Ω four-band resistor at ±5% is brown, black, brown, gold.
How to interpret your result
Ideal resistive DC arithmetic and supported four-band nominal codes only. No AC impedance, circuit safety, wiring design or component-rating approval. The examples identify the method and input basis, so the result can be checked without guessing a hidden convention.
For different inputs or formulas, use Ratio Calculator; Decimals Calculator; Scientific Notation Calculator.
Related questions this calculator covers
- ohm calculator
- ohm’s law calculator and resistor color codes
- ohm load calculation
- 100 ohm resistor color code
Scenario comparison
| Scenario | What it shows |
|---|---|
| 12 V and 0.5 A | 24 Ω and 6 W. |
| 12 V and 24 Ω | 0.5 A and 6 W. |
| 1,000 Ω with gold tolerance | brown, black, red, gold. |
Common mistakes to avoid
- Entering milliamperes as amperes.
- Treating a nonlinear or AC load as an ideal DC resistor.
- Inferring a resistor’s power rating from its color bands.
Substitute the same inputs into the disclosed equation and compare with this example: 12 V across a load carrying 0.5 A implies 24 Ω and 6 W. A 100 Ω four-band resistor at ±5% is brown, black, brown, gold. Keep the method, units and source assumptions with any recorded result.
Authoritative reference and additional source reference. Ideal resistive DC arithmetic and supported four-band nominal codes only. No AC impedance, circuit safety, wiring design or component-rating approval.What can affect the result?
Ideal resistive DC relationship
Ohm’s law here describes an ideal resistive direct-current load. The power output uses voltage times current. The calculation does not model AC reactance, phase angle, nonlinear devices, switching behavior or temperature-dependent resistance. An LED, battery or motor is not necessarily a constant resistor across every operating condition. The result is useful for checking a stated resistive relationship, but it cannot establish whether a circuit is safe or whether a power supply will behave ideally.
Four-band code from a nominal value
Color-code mode accepts resistance in ohms and one of the implemented tolerance choices. It uses two significant digits plus a multiplier. A nominal 100 Ω value is digits one and zero with a times-ten multiplier. A 1 kΩ value is 1,000 Ω, giving a times-one-hundred multiplier. Values requiring more than two significant digits are rejected instead of rounded silently to a different resistor. Five-band devices and manufacturer-specific markings need their own specification.
Verification and component selection
Band colors describe nominal resistance and tolerance; they do not give power rating, voltage rating, package suitability or operating temperature limits. Check the component datasheet and measure resistance using appropriate equipment in a safe condition. The calculated dissipated power is a mathematical load figure, not a recommendation to use a resistor with an equal nameplate rating. Derating, thermal environment and the intended circuit require qualified design review when consequential.
Watt and ampere conversion modes
Select watts to amps or amps to watts for DC, single-phase AC or balanced three-phase AC. Enter voltage and, for AC, a verified power factor above zero and at most one. Three-phase uses line-to-line RMS voltage and line current. Watts are real power; apparent VA and mechanical output are different quantities. There is no assumed motor efficiency, circuit ampacity, breaker size or installation design. Review the nameplate basis instead of treating a conversion as equipment approval.
Privacy and browser processing
Values entered on this page are processed in the current browser session. SolvePilot does not require an account and does not receive the values entered into the calculator. Refreshing or closing the page clears the working values unless the browser itself restores a previous session. Avoid entering identifying or account information because the calculation needs summary values only.
Accuracy and verification
Accuracy depends first on input quality. Confirm definitions, scales, dates and source information before entering a value. Keep an independent record of any result used for planning because this page does not create an official statement or retain a calculation history.
Limits of this estimate
Ideal resistive DC arithmetic and supported four-band nominal codes only. No AC impedance, circuit safety, wiring design or component-rating approval.
Sources and review information
Frequently asked questions
How do I calculate voltage?＋
For a resistive DC relationship, multiply current in amperes by resistance in ohms. Select current and resistance mode and use those units. A 0.5 A current through 24 Ω gives 12 V. This does not model a non-resistive or alternating-current load.
What is the 100 ohm resistor color code?＋
For a four-band resistor at the selected ±5% tolerance, the code is brown, black, brown, gold. The first two bands form ten and the third multiplies by ten. Change the tolerance selection when the component’s specified tolerance differs.
What is the 1k ohm resistor color code?＋
A 1 kΩ value means 1,000 Ω. In four-band ±5% form, it is brown, black, red, gold. A five-band precision component uses a different significant-digit format, so compare the actual device’s band count and datasheet.
Can this size mains wiring?＋
No. Wiring requires applicable electrical rules, installation conditions, protection and qualified assessment. Ohm’s law arithmetic cannot select a safe cable, breaker or fuse. Do not treat the displayed current or power as installation instructions.
Why is a color-code value rejected?＋
The implemented four-band format needs exactly representable two-significant-digit resistance and a supported multiplier. A value such as 123 Ω cannot be represented by that format without changing it. Use the appropriate five-band specification rather than accepting an undisclosed approximation.
How does the watt and ampere calculator convert AC values?＋
Single-phase real power is RMS voltage times RMS current times power factor. Balanced three-phase real power also uses √3 and line-to-line voltage. Divide real watts by the corresponding voltage and factor to get amps. These ideal formulas do not size protective devices or assess unbalanced loads.