Resistor network calculator
Total resistance of a circuit in series and in parallel.
Fill in the fields and the result will appear here automatically.
Find the equivalent resistance of one series chain or one parallel group of ideal resistors. Enter every rating in ohms without mixing Ω and kΩ. The result describes the voltage-to-current ratio of that group; it does not calculate each resistor's dissipation, heating or an arbitrary bridge circuit.
How it works
Formula and logic
Series current is common: U = I·ΣR, hence Req = ΣR. Parallel voltage is common: I = U·Σ(1/R), hence Req = 1/Σ(1/R). Two equal resistors R give R/2 in parallel and 2R in series. Positive inputs exclude a zero-resistance short from this model.
Example
470 Ω and 470 Ω give 940 Ω in series or 235 Ω in parallel. For 100, 220 and 330 Ω in parallel, 1/R = 1/100 + 1/220 + 1/330 = 29/1650, so R = 1650/29 ≈ 56.897 Ω.
Fields and units
- Resistances in ohms — one per line or separated by spaces — Ω
- Connection — list option
How to use
- — Select series or parallel connection.
- — Enter 2 to 256 positive ratings in Ω, separated by spaces or semicolons; the list is limited to 16 384 characters.
- — A decimal point or comma inside a number is accepted: 4,7 is one rating. For two ratings use 4; 7.
- — Compare with the extrema: series resistance exceeds the maximum and parallel resistance is below the minimum.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- OpenStax: common series current and parallel voltage
- Limitation
- Ideal constant resistances. Tolerances, temperature dependence, dissipation and electrical safety are not checked.
FAQ
Why is series resistance larger and parallel resistance smaller?
The sum of at least two positive resistances exceeds each one. In parallel, other positive conductances add to any one branch, so the reciprocal is below the smallest resistance.
Can I type 4.7 kΩ?
Unit suffixes are not parsed. Enter 4700 Ω as 4700. A value of 4.7 means 4.7 Ω; spaces or semicolons clearly separate multiple ratings.
Can every circuit be reduced with these two operations?
No. Actual series and parallel subgroups can be reduced step by step. A bridge generally needs Kirchhoff's laws or another circuit analysis; a list of ratings does not specify its connections.
Do resistor power ratings add?
This tool does not calculate dissipation. Distribution depends on resistances and connections, while permissible dissipation depends on component ratings and cooling. Two 0.25 W resistors do not always form a safe 0.5 W equivalent.
What about zero, one resistor or an enormous list?
This task requires at least two strictly positive ratings. A single resistor equals itself but is outside the group calculation. The 256-rating and 16 384-character limits are input limits, not physical laws.