Buoyancy Calculator
Compare an object’s weight with displaced-fluid buoyancy. Enter displacement directly or estimate whether a uniform object floats, sinks or is neutrally buoyant.
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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
Archimedes’ principle makes buoyancy equal to the weight of displaced fluid. A freely floating body displaces mass/rho volume. If that required volume exceeds the whole object volume, buoyancy is insufficient and the object sinks in this model.
Buoyancy=ρfluid gVdisplaced; weight=mg; floating displaced fraction=ρobject/ρfluid
Worked example
A1kg object with external volume2L in water of1000kg/m³ floats half submerged. At1L displacement the buoyancy is9.8N, equal to its weight.
Assumptions and input details
Mass, total volume and fluid density must be positive; entered displacement can be zero but cannot exceed external volume. Assume uniform fluid, a rigid nonporous external volume, no surface tension or trapped-fluid changes, andg>0. A sinking body’s displayed force uses full submersion; the actual depth-time motion is not calculated. Neutral buoyancy does not imply a stable surface position. Entered base-unit magnitudes are limited to1e12 unless a tighter limit is stated. Results use floating-point arithmetic. These are ideal-model estimates, not equipment load ratings.
References: OpenStax Archimedes’ principle
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
The 19 mass definitions distinguish avoirdupois and troy measures, metric and regional measures. Japanese kin is 600 g; mainland Chinese shijin is 500 g.
The 36 volume definitions distinguish US liquid, US dry and Imperial measures. Cups carry an explicit definition. Japanese shō is 2401/1331 L and a gō is one tenth of it; the explicitly labelled 180 mL rice cup is separate.
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 · UK Imperial definitions · 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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