Bifilar Pendulum Inertia Calculator
Estimate yaw mass moment of inertia from a small-angle period of a symmetric bifilar suspension.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Use equal top/bottom string spacing and a level suspended body in the small-yaw-angle limit.
I=m g (full spacing/2)² period²/(4π² string length)
Worked example
Doubling measured period multiplies the inferred inertia by four when mass and geometry stay fixed.
Assumptions and input details
Two equal parallel massless strings, centered mass, no swing/twist coupling or damping correction. Gravity is conventional9.80665 m/s². Total suspended inertia includes fixtures; no automatic tare subtraction or measurement certification.
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
The 19 mass definitions distinguish avoirdupois and troy measures, metric and regional measures. Japanese kin is 600 g; mainland Chinese shijin is 500 g.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
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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