Calculate total resistance of series resistors with voltage division. Supports up to 8 resistors with voltage drops, power dissipation, and visual breakdown of each resistor.
When resistors are connected in series, the total resistance is simply the sum: R_total = R₁ + R₂ + ... + Rₙ. The same current flows through each resistor, but the voltage divides across them in proportion to their resistance values. This voltage division principle is the foundation of voltage dividers, biasing networks, and current-limiting circuits.
Understanding series resistor networks is fundamental to circuit design. The voltage across each resistor equals V_n = I × R_n, where the total current I = V_supply / R_total. The power dissipated by each resistor is P_n = I² × R_n. These calculations become tedious with multiple resistors, especially when checking power ratings.
This calculator handles up to 8 series resistors, automatically computing the total resistance, current, individual voltage drops, power dissipation, and percentages. A visual bar chart shows how the supply voltage is divided, and a parallel equivalent is shown for comparison. It is an essential tool for electronics hobbyists, students, and engineers.
While adding series resistances is straightforward, computing individual voltage drops and power dissipation for each resistor requires multiple steps per component. With 4+ resistors, manual calculation is tedious and error-prone. This calculator shows the complete picture: total resistance, current, per-resistor voltage drops and power, and visual voltage distribution — all instantly updated.
Total Resistance: R_total = R₁ + R₂ + ... + Rₙ Current: I = V_supply / R_total Voltage across Rₙ: Vₙ = I × Rₙ = V_supply × Rₙ / R_total Power per resistor: Pₙ = I² × Rₙ Total Power: P_total = V_supply × I = V²_supply / R_total
Result: R_total = 3670 Ω, I = 3.27 mA
Three resistors of 1kΩ, 2.2kΩ, and 470Ω in series sum to 3670Ω. With 12V applied, I = 12/3670 ≈ 3.27 mA. Voltage drops: V₁ = 3.27V (1kΩ), V₂ = 7.19V (2.2kΩ), V₃ = 1.54V (470Ω). These sum to 12V as expected.
The voltage divider is one of the most fundamental circuits in electronics. Two series resistors create a predictable output voltage that is a fraction of the input. This principle is used in sensor circuits (resistive dividers with thermistors or photoresistors), biasing transistor bases, setting reference voltages, and reading analog signals with ADCs that have limited input ranges.
Each resistor in a series string dissipates power according to P = I²R. Since the current is the same through all, the highest-value resistor dissipates the most power. Always verify that each resistor is rated for its individual power dissipation, not just the total. Standard resistors come in 1/8W, 1/4W, 1/2W, and 1W ratings.
When you need a specific resistance not available in standard (E12 or E24) series, combine series resistors. For example, 1.5kΩ + 3.3kΩ = 4.8kΩ, close to the non-standard value of 4.7kΩ. This technique is particularly useful for precision circuits where the exact E96 or E192 value isn't available in your parts bin.
In series, the same current flows through each resistor. Each one creates a voltage drop (V = IR), and by Kirchhoff's Voltage Law, these drops must sum to the total voltage. Since I is the same for all, V_total = I×R₁ + I×R₂ + ... = I×(R₁+R₂+...), so R_total = R₁+R₂+...
Series: R_total = R₁ + R₂ (always larger than either). Parallel: 1/R_total = 1/R₁ + 1/R₂ (always smaller than the smallest). Series shares current; parallel shares voltage.
A voltage divider is two (or more) series resistors where the output voltage is taken from the junction between them. V_out = V_in × R₂/(R₁+R₂). It is the simplest way to reduce a voltage to a desired level.
Yes, this is the most common use. The resistor value is R = (V_supply − V_LED) / I_LED. For example, with 5V supply, 2V LED, and 20mA current: R = (5−2)/0.02 = 150Ω.
Each resistor's actual value can vary by its tolerance. In the worst case, all could be high or all low, so the total tolerance percentage is the same as individual resistors. Statistically, errors tend to average out.
Use series when you need higher resistance, voltage division, or current limiting. Use parallel when you need lower resistance, current sharing, or higher power handling (the power capacity of parallel resistors adds up).