Independent Series and Parallel Reliability Calculator
Combine component survival probabilities for an all-required series system or an at-least-one-required parallel system.
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Result
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Calculation steps
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How to calculate
Multiply component reliabilities for a series success condition. For a parallel system, multiply component failure probabilities and subtract from one.
Series R=product Ri; parallel R=1−product(1−Ri)
Worked example
Two independent components at 90% and 80% survival have series reliability 72% and parallel reliability 98% over the same mission interval.
Assumptions and input details
One to one hundred probabilities, each from 0 to 100%. All refer to the same time interval and statistically independent failures. Parallel means at least one working component is sufficient, with perfect switching and no common-cause failure. No repairs, standby aging, capacity thresholds or dependency model. These calculations do not establish safety or observed product reliability.
References: NIST: series reliability · NIST: parallel reliability
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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