Ohms Law Calculator

Ohms Law Calculator

Calculate voltage, current, resistance, and power using Ohms Law. Perfect for electronics, electrical engineering, and circuit design.

What would you like to calculate?

Quick Circuit Presets

For energy calculations (1 hour = 3600s)

Ohms Law Formula

V = I × R
I = V ÷ R
R = V ÷ I
P = V × I

Voltage Safety Levels

Low Voltage
50V
Safe for direct contact
Medium Voltage
120V
Standard household
High Voltage
240V
Industrial power
Dangerous
1000V
Professional use only

About Ohms Law Calculator

This calculator uses Ohms Law (V = I × R) and power formulas to solve electrical circuit problems. It can calculate any missing value when you know two of the three basic electrical quantities: voltage, current, and resistance. The calculator also computes power, energy consumption, and provides safety information based on voltage levels. Perfect for electronics hobbyists, students, and electrical engineers.

About Ohms Law Calculator

Our comprehensive Ohms Law calculator helps electronics enthusiasts, students, and electrical engineers solve circuit problems with precision and ease. This essential tool provides accurate calculations for voltage, current, resistance, and power, supporting both educational and professional electrical applications.

What It Calculates

  • Voltage (V): Electrical potential difference in volts
  • Current (I): Electrical current flow in amperes
  • Resistance (R): Opposition to current flow in ohms
  • Power (P): Electrical power consumption in watts
  • Energy (E): Total energy consumed in joules
  • Efficiency: Circuit efficiency percentage

Ohms Law Fundamentals

Basic Formula
  • V = I × R: Voltage equals current times resistance
  • I = V ÷ R: Current equals voltage divided by resistance
  • R = V ÷ I: Resistance equals voltage divided by current
  • Linear Relationship: Direct proportionality
  • Unit Consistency: Volts, amperes, and ohms
  • Fundamental Law: Basis of electrical engineering
Power Formulas
  • P = V × I: Power equals voltage times current
  • P = V² ÷ R: Power equals voltage squared divided by resistance
  • P = I² × R: Power equals current squared times resistance
  • Energy = P × t: Energy equals power times time
  • Efficiency: Output power divided by input power
  • Power Loss: I²R losses in conductors

Understanding Your Results

Voltage

Electrical potential

Current

Electron flow rate

Resistance

Flow opposition

Power

Energy per second

How to Use

Select the calculation type (voltage, current, resistance, or power), enter the known values, and the calculator will automatically compute the missing quantities. The tool provides comprehensive results including power, energy, efficiency, and safety information for informed circuit design.

Electrical Units and Prefixes

Voltage Units:

  • 1 mV = 0.001 V (millivolt)
  • 1 V = 1 volt (base unit)
  • 1 kV = 1,000 V (kilovolt)
  • 1 MV = 1,000,000 V (megavolt)

Current Units:

  • 1 μA = 0.000001 A (microampere)
  • 1 mA = 0.001 A (milliampere)
  • 1 A = 1 ampere (base unit)
  • 1 kA = 1,000 A (kiloampere)

Circuit Analysis Applications

Series Circuits
  • Current: Same through all components
  • Voltage: Divides across components
  • Resistance: Adds together (Rtotal = R1 + R2 + ...)
  • Power: Sum of individual power values
  • Voltage Drop: Proportional to resistance
  • Applications: LED strings, voltage dividers
Parallel Circuits
  • Voltage: Same across all components
  • Current: Divides among components
  • Resistance: Reciprocal sum (1/Rtotal = 1/R1 + 1/R2 + ...)
  • Power: Sum of individual power values
  • Current Division: Inversely proportional to resistance
  • Applications: Household wiring, power distribution

Safety Considerations

  • Low Voltage: Below 50V - generally safe for contact
  • Medium Voltage: 50V to 1000V - requires caution
  • High Voltage: Above 1000V - professional handling only
  • Current Limits: 10mA can cause muscle contraction
  • Power Ratings: Check component specifications
  • Protection Devices: Use fuses and circuit breakers

Common Circuit Components

Resistors

Limit current flow

Capacitors

Store electrical charge

Inductors

Store magnetic energy

Practical Applications

  • LED Circuits: Calculate current-limiting resistors
  • Voltage Dividers: Create reference voltages
  • Power Supplies: Determine component ratings
  • Audio Systems: Impedance matching calculations
  • Motor Control: Current and power requirements
  • Battery Circuits: Load resistance and capacity

Advanced Concepts

  • AC vs. DC: Ohms Law applies to both
  • Impedance: Complex resistance in AC circuits
  • Reactance: Frequency-dependent opposition
  • Power Factor: Real vs. apparent power
  • Skin Effect: High-frequency current distribution
  • Temperature Effects: Resistance changes with heat

Calculation Tips

  • Unit Consistency: Always use compatible units
  • Significant Figures: Maintain appropriate precision
  • Verification: Cross-check with known relationships
  • Limits: Check for unrealistic values
  • Context: Consider practical constraints
  • Documentation: Keep calculation records

Common Calculation Mistakes

  • Unit Confusion: Mixing volts, millivolts, etc.
  • Formula Errors: Using wrong Ohms Law variant
  • Sign Errors: Incorrect positive/negative values
  • Precision Errors: Over-rounding or under-rounding
  • Context Ignorance: Not considering circuit type
  • Safety Neglect: Ignoring voltage/current limits
Pro Tip

Always verify your Ohms Law calculations by checking that the relationships make sense. Remember that power increases with both voltage and current, and resistance limits current flow. For safety, always check component ratings and use appropriate protection devices. When working with complex circuits, break them down into simpler parts and apply Ohms Law step by step. Keep a reference of common component values and always double-check your units and calculations.