Calculate total resistance for two or more resistors in series, with optional shared current, total power, and per-resistor voltage-drop breakdown from an entered supply voltage.
Last updated
Also in Basic Circuits
Basic circuits
A series resistor calculator is useful when you need more than a simple sum. This version totals two or more resistor values in mixed units, and when a supply voltage is entered it also reports the shared current, total power, and the voltage drop across each resistor in the chain.
This page accepts two or more resistor values, normalizes mixed ohm, kilohm, and megohm entries into ohms, and sums them into one total series resistance.
An optional supply voltage adds the shared circuit current, total power, and a branch-by-branch voltage-drop table so you can inspect how the source is divided across the chain.
In a series path the same current must pass through each resistor, so the total resistance is the direct sum of the valid branch resistances. There is no reciprocal step as there is in a parallel network.
That direct sum makes series chains useful for current limiting, simple drop networks, and first-pass checks where the total path resistance matters most.
Rtotal = R1 + R2 + ... + Rn
Series resistances add directly because each resistor sits in the same current path.
Once supply voltage is known, the entire chain shares one current set by the source voltage and the total series resistance. Each resistor then gets a voltage drop equal to that shared current multiplied by its own resistance.
The voltage-drop table is useful for verifying divider-style behaviour, spotting which resistor takes most of the source voltage, and estimating resistor dissipation.
I = V / Rtotal
The shared current comes from Ohm's law applied to the full series path.
Vdrop = I × Rbranch; P = V × I
Each resistor's drop scales with its resistance, while power follows from the same shared current and voltage relationships.
This calculator treats the network as ideal resistors in a simple series chain. It does not model tolerance spread, heating, frequency effects, parasitics, or source sag.
Use it as a planning and educational reference. If the network includes reactive parts, nonlinear devices, or tight thermal limits, move to the model that captures those effects explicitly.
Frequently asked questions
Because a true series path has only one current path. The same current must pass through every resistor in the chain.
Because the same current flows through each resistor, and voltage drop in each branch is V = I × R. Higher resistance therefore creates a larger drop at the same current.
Yes. This calculator normalizes every resistor into ohms first, then totals the series resistance and derives the optional current, power, and voltage drops from that common base.
Related
These related calculators come from the same leaf category, nearby sibling categories, or the same top-level topic.
Calculate equivalent resistance for two or more resistors in parallel, with total conductance and optional branch current and power breakdown from a shared supply voltage.
Solve for voltage, current, resistance, and power from any two known values using Ohm's Law (V = IR) and the power equation (P = IV).
Decode 4-band and 5-band resistor colour codes, or calculate total resistance for resistor lists in series and parallel.
Calculate the unloaded output voltage of a two-resistor divider from source voltage and resistor values, including divider current and resistor power dissipation.
