Resistance Calculator | Calculate Ohm's Law & Color Codes

Ohm's Law Calculator

Voltage (V)

Volts

Current (I)

Amps

Resistance (R)

Ohms

Power (P)

Watts

Calculated Values: Enter any two values

Ohm's Law: V = I × R | P = V × I

Resistor Color Code Decoder

1st Band

2nd Band

Multiplier

Tolerance

Resistance Value: 1.5KΩ ±5%

Range: 1.425KΩ - 1.575KΩ

Series & Parallel Resistance Calculator

Resistor 1 (R1)

Resistor 3 (R3)

Resistor 2 (R2)

Resistor 4 (R4)

Series Resistance

800 Ω

Parallel Resistance

47.06 Ω

Voltage Divider

Input Voltage (Vin)

Resistor 1 (R1)

Resistor 2 (R2)

Output Voltage (Vout)

8 V

Formula: Vout = Vin × (R2 / (R1 + R2))

Power Calculation

Resistance (R)

Voltage (V)

Power (P)

1.44 W

Formula: P = V² / R

Current Calculation

Voltage (V)

Resistance (R)

Current (I)

0.12 A

Formula: I = V / R

SMD Resistor Decoder

SMD Code (3 or 4 digit)

Resistance Value

10 KΩ

3-digit: first two are value, third is multiplier

How to Use the Resistance Calculator: A Complete Guide

Our resistance calculator is a comprehensive tool for electronics enthusiasts, engineers, and students. Here's how to make the most of each feature:

1. Ohm's Law Calculator

Enter any two values (voltage, current, resistance, or power) and the calculator will automatically compute the other two values in real-time. This is based on the fundamental Ohm's Law formulas: V = I × R and P = V × I.

2. Resistor Color Code Decoder

Select the color bands from the dropdown menus to decode a resistor's value. The visual resistor display updates instantly as you change band colors. The calculator shows the resistance value, tolerance, and the possible value range.

3. Series & Parallel Resistance Calculator

Enter values for up to four resistors to calculate both the series (R_total = R1 + R2 + ...) and parallel (1/R_total = 1/R1 + 1/R2 + ...) equivalent resistances. All calculations update in real-time as you modify values.

4. Voltage Divider Calculator

Determine the output voltage of a voltage divider circuit by entering the input voltage and two resistor values. The formula Vout = Vin × (R2 / (R1 + R2)) is applied automatically.

5. Additional Calculators

Use the power calculator to find power dissipation (P = V²/R), the current calculator to find current flow (I = V/R), and the SMD resistor decoder to interpret surface-mount device codes.

Pro Tip: All calculators work in real-time. Simply change any input value and results update instantly. Use the "Reset All" button to clear all inputs at once.

Applications of Resistance Calculations

Circuit Design: Determine appropriate resistor values for voltage dividers, current limiting, and pull-up/down resistors.
Troubleshooting: Verify resistor values and calculate expected voltages/currents in circuits.
Education: Learn and practice Ohm's Law and circuit analysis principles.
Component Selection: Choose correct resistors for specific applications based on power ratings and values.

This tool is completely free and works directly in your browser with no installation required. Bookmark it for quick access during your electronics projects!