Series Resistance Calculator
Enter three resistors R₁, R₂, R₃ and instantly get the series equivalent R = R₁ + R₂ + R₃. R₁=6 Ω, R₂=3 Ω, R₃=1 Ω → R=10 Ω.
Input Data
Results
At a glance:Series resistance means connecting several resistors end-to-end in a single path, so current flows through each in turn. The equivalent total resistance is the value of one resistor that could replace the whole group. Two key facts: (1) the same current flows through every resistor (only one path, no branching); (2) the supply voltage is divided across the resistors, each drop proportional to its resistance (larger resistor gets more voltage). The calculation is simply the sum: R=R₁+R₂+R₃+… (all in Ω). Example: R₁=6 Ω, R₂=3 Ω, R₃=1 Ω → R=10 Ω. A key property: the series total is always greater than the largest single resistor, because current must pass through every resistor and the opposition adds up. This is the opposite of parallel (which gets smaller). Applications: (1) voltage divider — split a higher voltage proportionally; (2) current-limiting resistor — in series with an LED or buzzer to protect it; (3) potentiometer — vary the series resistance; (4) voltmeter range extension — series a large resistor; (5) older Christmas light strings — one broken bulb kills the whole string. Notes: series is direct addition, unlike parallel 'product over sum'; current is identical but voltage splits by resistance ratio; use consistent Ω units; enter 0 for an unused third resistor.
Formula
Series: R = R₁ + R₂ + R₃ + … (Ω)
Series total is always > the largest single resistor
Series current is the same: I = V/R
Voltage division: Vₙ = I·Rₙ (proportional to resistance)
$$R = R_1 + R_2 + R_3$$How to Use
- Enter the first resistor R₁ (Ω).
- Enter the second and third resistors R₂, R₃ (0 if unused).
- The series equivalent total R is shown instantly.
Case Studies
Three resistors in series
R₁=6 Ω, R₂=3 Ω, R₃=1 Ω.
R = R₁ + R₂ + R₃ = 6 + 3 + 1.
= 10 Ω (larger than the biggest, 6 Ω).
Two resistors in series (divider)
R₁=4 Ω, R₂=6 Ω, R₃=0 (unused).
R = 4 + 6 = 10 Ω; at 10 V the current I = 1 A.
R₂ drops V₂ = I·R₂ = 6 V (larger resistor, larger drop).
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.