Ohm's Law Solver
Solve voltage, current, resistance, and power relationships. Free MyCalcsWorld science tool for students and makers.
Results
Voltage (V)
- Current (A)
- 2
- Resistance (Ω)
- 6
- Power (W)
- 24
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Educational estimates · not financial advice · free, no signup
Formula / how it works
V = IR, P = VI. Leave the unknown blank.
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Textbook physics/chemistry, SI-friendly. The Ohm's Law Solver on MyCalcsWorld is for homework checks and first-cut estimates under idealized assumptions unless noted. What it does: Solve for voltage, current, or resistance (and power) given any two. Typical inputs: Voltage V, Current I (amps), Resistance R (ohms). Demo defaults (current i (amps) 2, resistance r (ohms) 6) currently resolve to Voltage (V) 12 in the live panel — change any field to explore sensitivity. Who it helps: lab students, makers, and engineers doing first-cut checks with textbook identities before applying real tolerances.
When to use / who it helps
- Homework checks for V = IR and P = VI.
- Sizing a resistor for an LED with a series estimate.
- Sanity-checking a bench measurement.
- Use the Ohm's Law Solver for homework checks and first-cut design estimates under textbook assumptions.
- Keep SI (or the form’s stated units) consistent — a wrong unit ruins precision.
How to use
Steps
- Enter the two known quantities the form requests.
- Leave unknowns blank or select solve mode if offered.
- Read V, I, R, and/or P.
- Apply safety margin for real parts.
- Open the Ohm's Law Solver on MyCalcsWorld and skim the labeled fields before you type.
- Set Voltage V.
How to interpret results
- V = I R; P = V I = I²R = V²/R for ohmic DC.
- Results assume ideal resistors.
- Educational / first-cut only.
- Each result is driven only by the labeled inputs (Voltage V, Current I (amps), Resistance R (ohms)); anything not on the form (fees, holidays, clinical adjustments) is outside this estimate.
- Results assume the idealized model stated in the formula notes (constant parameters, ohmic behavior, etc.).
Common mistakes & gotchas
- Applying ohmic assumptions to diodes/LEDs without the forward drop model.
- Mixing mA and A.
- Ignoring power ratings when current is high.
- Mixing SI and customary units across: Voltage V, Current I (amps), Resistance R (ohms).
- Ignoring that textbook models omit friction, temperature drift, or non-ohmic behavior.
Worked example
Worked example — 12 V across 220 Ω
- V = 12, R = 220.
- I = V/R ≈ 0.0545 A ≈ 54.5 mA.
- P = V I ≈ 0.655 W — choose a resistor with margin.
- Open the Ohm's Law Solver (ohms law solver) and note the starting defaults (current i (amps) 2, resistance r (ohms) 6).
Result: With defaults (current i (amps) 2, resistance r (ohms) 6), the Ohm's Law Solver shows: Voltage (V) 12.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
V = IR, P = VI. Leave the unknown blank.
Frequently asked questions
Does this work for AC?
Only in a simplified resistive sense. AC circuits with reactance need impedance methods.
How do I include an LED?
Subtract LED forward voltage from supply, then size the series resistor with the remaining voltage.
Why is power important?
Resistors have watt ratings; exceeding them overheats parts.
Is this a substitute for a multimeter?
No — measure real circuits with proper instruments and safety practice.
What does the Ohm's Law Solver on MyCalcsWorld actually compute?
Solve for voltage, current, or resistance (and power) given any two. You enter Voltage V, Current I (amps), Resistance R (ohms), and the result panel updates in your browser.
What inputs does the Ohm's Law Solver need?
The Ohm's Law Solver asks for: Voltage V; Current I (amps); Resistance R (ohms).
What results does the Ohm's Law Solver show?
The panel reports Voltage (V). Each figure is recalculated whenever you change an input, so you can compare scenarios side by side.
Does this include real-world losses and tolerances?
Usually not. Textbook identities assume ideal conditions unless a field asks for efficiency, friction, or tolerance. Apply your own safety factors for designs that affect safety or compliance.
Textbook formulas under ideal assumptions. For safety-critical, structural, or regulated work, verify with a qualified engineer and the governing standards. Full disclaimer