Formula Used
Ohm's law: V = I × R
Branch current: In = V / Rn
Branch power: Pn = V × In = V² / Rn
Total current: IT = I1 + I2 + I3 + ...
Total conductance: GT = 1/R1 + 1/R2 + 1/R3 + ...
Equivalent resistance: Req = 1 / GT
Total load power: PT = V × IT
Source drop: Vdrop = IT × Rsource
Temperature adjustment: Radjusted = R × [1 + α × 10-6 × ΔT]
How to Use This Calculator
Enter two or more branch resistance values. Separate them with commas, spaces, or new lines.
Select the resistance unit used by the branch list.
Add branch labels when you want named output rows.
Enter supply voltage if it is known. The calculator gives voltage first priority.
Leave voltage blank to solve from known total current.
Leave voltage and current blank to solve from known load power.
Add source resistance to estimate voltage drop and source loss.
Use tolerance and temperature fields for advanced practical estimates.
Press Calculate. The result appears above the form and below the header.
Use the CSV or PDF button to save the current result.
Parallel Circuit Insight
A parallel circuit gives each branch the same load voltage. Current separates through the available branch paths. Lower resistance branches carry more current. Higher resistance branches carry less current. This calculator helps compare those branch values before a circuit is built or checked.
Why This Calculator Helps
Manual parallel work can become slow when many branches exist. The reciprocal resistance rule also creates rounding mistakes. This tool accepts many resistance values at once. It adjusts values for tolerance and temperature rise. It can solve from supply voltage, known total current, or known total load power. That makes it useful for design checks, repair notes, lab worksheets, and quick teaching examples.
Electrical Meaning
Ohm's law states that voltage equals current times resistance. In a parallel network, every branch sees the same load voltage. Total current equals the sum of branch currents. Total conductance equals the sum of branch conductances. Equivalent resistance is the reciprocal of total conductance. Because conductance adds, total resistance is always less than the smallest branch resistance.
Advanced Inputs
The source resistance field estimates internal or wire resistance. When a source voltage is entered, the load voltage is reduced by the source drop. Tolerance creates a possible equivalent resistance range. Temperature coefficient changes resistance by parts per million per degree. These options make the result closer to a real electrical situation. They are still estimates, so final designs should follow rated parts and safety rules.
Interpreting The Output
The summary shows equivalent resistance, conductance, load voltage, total current, and total load power. The branch table shows current, power, and current share for each path. A branch with high power may need a larger wattage rating. A branch with a large current share may need thicker wiring or a lower heat rise. The source section shows source drop and source loss when source resistance is used.
Practical Use
Start by entering resistor values in ohms, kilohms, or megohms. Add labels when the circuit has named branches. Enter the known value you trust most. Voltage has first priority. Current is used next. Power is used last. Review warnings if extra known values do not match the solved network. Then export the report for records and sharing safely.
FAQs
What does this parallel circuit calculator solve?
It solves equivalent resistance, total conductance, branch currents, branch powers, total current, load power, source drop, and source loss. It can start from voltage, total current, or load power.
Why is equivalent resistance lower in parallel circuits?
Parallel branches add more paths for current. More paths raise total conductance. Since equivalent resistance is the reciprocal of conductance, the final resistance becomes lower than the smallest branch value.
Can I enter many resistors at once?
Yes. Enter values separated by commas, spaces, semicolons, pipes, or new lines. The calculator reads them as branch resistances in the same parallel network.
Which known value has priority?
Supply voltage has first priority. If voltage is blank, known total current is used. If both voltage and current are blank, known load power is used to solve the network.
What is source resistance?
Source resistance represents internal supply resistance or wiring resistance. It creates a voltage drop before the load. Enter zero when you want an ideal source calculation.
How does tolerance affect the answer?
Tolerance estimates a low and high equivalent resistance range. It applies the same percent change to each branch after temperature adjustment. Real parts may vary by rating and batch.
What does temperature coefficient mean?
Temperature coefficient shows how resistance changes with heat. It is entered in parts per million per degree Celsius. A zero value ignores temperature effects.
Can I export the result?
Yes. After calculation, use the CSV button for spreadsheet data. Use the PDF button for a printable report containing summary and branch values.