Instantly calculate resistance, current, voltage, and power in series, parallel, and mixed electrical circuits using our free interactive tools.
Calculate voltage, current, resistance, or power using Ohm's Law (V = IR, P = VI). For more advanced power calculations in AC systems, you might find our reactive and apparent power converter helpful for understanding the relationship between real, reactive, and apparent power.
Calculate total resistance of resistors connected in series (Rtotal = R1 + R2 + ... + Rn). When working with real components, you may need to check standard values using our capacitor code calculator or determine appropriate wire sizes with the AWG to mm converter.
Calculate total resistance of resistors connected in parallel (1/Rtotal = 1/R1 + 1/R2 + ... + 1/Rn). This principle also applies to other components, and you can explore this further with our current divider calculator, which specifically addresses how current distributes in parallel branches.
Calculate total resistance of mixed series and parallel resistor networks.
Calculate output voltage of a voltage divider circuit (Vout = Vin × R2 / (R1 + R2)).
Calculate current through parallel branches (I1 = Itotal × R2 / (R1 + R2)).
Calculate electrical power using P = VI, P = I²R, or P = V²/R.
Calculate total capacitance for capacitors in series or parallel.
Calculate total inductance for inductors in series or parallel.
Compute total impedance in RLC AC circuits (Z = √(R² + (XL - XC)²)).
Determine the time constant τ = RC for charging/discharging capacitors. For more detailed analysis of circuit behavior over time, explore our transient analysis calculator, which provides deeper insight into how circuits respond to changes.
Compute τ = L/R for RL circuits.
| Calculator | Input Values | Result |
|---|---|---|
| Ohm's Law | V=12V, R=100Ω | I=120mA, P=1.44W |
| Series Resistor | R1=100Ω, R2=220Ω | Rtotal=320Ω |
| Parallel Resistor | R1=100Ω, R2=100Ω | Rtotal=50Ω |
| Voltage Divider | Vin=12V, R1=1kΩ, R2=2kΩ | Vout=8V |
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | 100 | |
| Brown | 1 | 101 | ±1% |
| Red | 2 | 102 | ±2% |
| Orange | 3 | 103 | |
| Yellow | 4 | 104 | |
| Green | 5 | 105 | ±0.5% |
| Blue | 6 | 106 | ±0.25% |
| Violet | 7 | 107 | ±0.1% |
| Gray | 8 | 108 | ±0.05% |
| White | 9 | 109 | |
| Gold | 10-1 | ±5% | |
| Silver | 10-2 | ±10% |
| Type | R1 (Ω) | R2 (Ω) | V (Volts) | Result |
|---|---|---|---|---|
| Series | 100 | 220 | 9V | Total R = 320Ω, I = 28.1 mA |
| Parallel | 100 | 220 | 9V | Total R ≈ 68.8Ω, I = 130.8 mA |
| Voltage Divider | 1kΩ | 2kΩ | 12V | Vout = 8V |
| Current Divider | 100Ω | 220Ω | 100mA | I1 = 68.75mA, I2 = 31.25mA |
| Power | 120Ω | 12V | P = 1.2W | |
| Capacitor Parallel | 10μF | 22μF | Ctotal = 32μF | |
| Inductor Series | 10mH | 22mH | Ltotal = 32mH |
These calculators implement fundamental electrical engineering principles used in circuit design, analysis, and troubleshooting. Each tool addresses specific circuit analysis needs. When designing practical systems, you may also need tools like the PCB trace width calculator for board layout or the thermistor resistance calculator for temperature sensing applications.
| Calculator | Primary Formula | Variables |
|---|---|---|
| Ohm's Law | V = I × R P = V × I = I²R = V²/R |
V: Voltage (V) I: Current (A) R: Resistance (Ω) P: Power (W) |
| Series Resistance | Rtotal = ΣRi | Ri: Individual resistors |
| Parallel Resistance | 1/Rtotal = Σ(1/Ri) | For two resistors: Rtotal = (R₁×R₂)/(R₁+R₂) |
| AC Impedance | Z = √[R² + (XL - XC)²] XL = 2πfL XC = 1/(2πfC) |
Z: Impedance (Ω) XL: Inductive reactance XC: Capacitive reactance f: Frequency (Hz) |
| Time Constants | τ = RC (RC circuit) τ = L/R (RL circuit) V(t) = V₀(1 - e-t/τ) |
τ: Time constant (s) 63.2% of final value at t=τ |
Assumptions Made in Calculations:
Applicable Ranges:
Parallel conductances (1/R) add directly because current divides among parallel paths. The reciprocal relationship Rtotal = 1/Σ(1/Ri) comes from combining conductances: Gtotal = ΣGi, where G = 1/R.
These calculations provide theoretical values assuming ideal components. Real-world accuracy depends on:
For prototyping, include ±10% margin; for production, perform worst-case analysis.
DC Analysis: Use for batteries, power supplies, digital circuits, and any circuit where frequency < 1 Hz or where reactive components don't affect operation.
AC Analysis: Essential for:
Time constants (τ) determine circuit speed:
After using these basic calculators, consider exploring more specialized tools such as the filter calculator tool for advanced frequency response analysis, or the op-amp gain calculator for amplifier design. For power system work, the power factor correction calculator can help optimize AC power delivery.
Note: These tools complement but do not replace professional circuit simulation software (SPICE, LTspice, etc.) for complex designs.