tooloctopus.

Parallel resistance calculator

For ideal resistors in parallel, 1/R = 1/R₁ + 1/R₂ + …

On your device · No account
Privacy details

Parallel resistance calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

Copy link includes the inputs you choose to share in the address. Anyone with that link can reopen them. Files and generated results are excluded. Password and key tools share settings only.

Spaces separate values; 1,000 is one value.

Answer

…

For ideal resistors in parallel, 1/R = 1/R₁ + 1/R₂ + …

More results
Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Saved scenario
Save the current answer, then change an input to compare. This clears when you leave.
Formula and assumptions
Enter positive resistances separated by commas or whitespace. This ideal DC calculation excludes temperature changes and parasitic effects.
In a list, use spaces, new lines, semicolons, or commas followed by a space. A comma between groups of three digits is a thousands separator.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
Scratch calculator
Use +, −, ×, ÷, parentheses and %. A percentage is divided by 100. This does not change the main tool.
Reset reloads the tool with its starting values and releases open files and device controls. Saved drafts stay on this device until you delete them.
Links include your inputs and settings. Anyone with the link can see them, so leave out private text. Files and generated results are left out; random draws run again.
Keyboard shortcuts
Updated 
Using Parallel resistance calculator
For ideal resistors in parallel, 1/R = 1/R₁ + 1/R₂ + …
Enter positive resistances separated by commas or whitespace. This ideal DC calculation excludes temperature changes and parasitic effects.
Next: Basic calculator
A worked example
With resistances (ohms) = 10 20 20, the equivalent resistance (ohms) is 5.
Before you use the result
Enter positive resistances separated by commas or whitespace. This ideal DC calculation excludes temperature changes and parasitic effects.
Cite this page
ToolOctopus. “Parallel resistance calculator.” Updated 2026-09-26. https://tooloctopus.com/parallel-resistance-calculator.
Add an access date if your instructions require one.
Citation formatting uses citeproc-js by Frank Bennett and Citation Style Language styles. Licence and source code.
Find a tool
Search by task. Use ↓ and ↑ to choose, Enter to open.