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Reference library Connections Sources University circle All areas of study / Measurement Topic All topics Quantities, units & constants · 22 Uncertainty & inference · 27 Calibration & standards · 38 Signals & measurement systems · 30 Measurement quality & decisions · 25 Shared & other concepts · 17
Mathematics & logic · Physics · Measurement Ratios and rates Distinguish part-to-part ratios, fractions of a whole and rates with units. Scale quantities together, compare unit rates, and explain when a relationship is proportional. Check zero cases, starting amounts and whether a result fits its context.
Definition → Mathematics & logic · Physics · Measurement Quantities and units Describe a quantity as a numerical value with a unit, and distinguish its physical kind from its dimension. Build length, area, volume and rate units, check meaningful combinations, and separate exact unit relations from measurement uncertainty.
Definition → Mathematics & logic · Physics · Measurement Unit conversions Convert quantities with exact unit ratios, track cancellation through compound units, and apply the correct powers to area and volume. Distinguish temperature readings from differences, check dimensions and context, and retain measurement uncertainty when reporting.
Method → Mathematics & logic · Physics · Measurement Estimation and uncertainty Distinguish exact model values, rounded approximations and estimates from measurements. Declare the rounding rule, preserve information through calculations and unit changes, and interpret resolution, precision, accuracy and the stated uncertainty type without turning a report’s digits into guaranteed bounds.
Definition → Mathematics & logic · Physics · Measurement Reading graphs Read a graph’s quantities, units, ticks and context before judging its visual impression. Calculate differences, reference-based percentages and interval rates from the represented values; distinguish legitimate zoom from distorted spacing; and keep samples, interpolation, missing information, uncertainty and causal explanations separate.
Method → Physics · Measurement Observables and measurement Choose the physical quantity you want to investigate, specify the point, event or location involved, and explain how a reading relates to that quantity.
Method → Physics · Information · Measurement Scientific records Build an inspectable physics record, test and revise a bounded cart model, preserve processing history, and plan findable data with appropriate sharing conditions.
Method → Physics · Measurement Speed of light in vacuum c denotes the speed of light in vacuum. Its numerical value is fixed exactly in SI units.
Definition → Physics · Measurement Planck constant h denotes the Planck constant. Its numerical value is fixed exactly in SI units.
Definition → Physics · Measurement Caesium-133 defining frequency ΔνCs denotes the unperturbed ground-state hyperfine transition frequency of caesium-133. Its numerical value is fixed exactly in SI units.
Definition → Mathematics & logic · Measurement Euclidean right triangles and the Pythagorean theorem In a Euclidean right triangle, squared leg lengths sum to the squared hypotenuse length.
Mathematical statement → Mathematics & logic · Measurement Confidence interval for a population mean A confidence level describes repeated-sampling coverage of an interval procedure.
Method → Measurement SI base units Seven named base units organize the SI quantity system.
Definition → Measurement SI decimal prefixes Prefix symbols specify decimal scale factors.
Definition → Measurement Metrological traceability Connect a result to a reference through documented calibrations.
Definition → Measurement · Mathematics & logic First-order uncertainty propagation Combine input uncertainty through a measurement model.
Method → Measurement · Physics · Mathematics & logic Dimensional consistency Use dimensions to detect impossible quantity equations.
Method → Physics · Measurement Electric current Current measures charge crossing a chosen surface per unit time.
Definition → Physics · Measurement Elementary charge The elementary charge has an exact SI numerical value.
Definition → Physics · Measurement Boltzmann constant The Boltzmann constant has an exact SI numerical value.
Definition → Measurement · Chemistry · Physics Avogadro constant The mole is linked to a specified number of entities.
Definition → Measurement · Physics SI defining luminous efficacy A specified frequency fixes the photometric SI reference.
Definition → Chemistry · Measurement Mole and amount of substance The mole counts specified entities using the exact Avogadro constant.
Definition → Measurement Calibration Relate indications to standards, then infer measurement results.
Definition → Measurement Type A and Type B uncertainty evaluation The classification describes how a component is evaluated.
Method → Measurement Expanded uncertainty and coverage A coverage factor scales standard uncertainty to a reported interval.
Method → Measurement · Mathematics & logic Covariance in uncertainty models Shared input variation belongs in the joint uncertainty description.
Method → Measurement Measurement models Specify how input quantities determine the measurand.
Method → Measurement · Information Monte Carlo uncertainty propagation Sample the joint input model to approximate the output distribution.
Method → Measurement Repeatability and reproducibility Precision depends on which measurement conditions are held or changed.
Definition → ← Back to entries Definition Source checked
Planck constant Physics Measurement
h denotes the Planck constant. Its numerical value is fixed exactly in SI units.
Key knowledge h = 6.626 070 15 × 10⁻³⁴ J s, exactly by the SI definition.
Reference values h 6.62607015e-34 J s
Exact value · SI definition Values and equations h = 6.626 070 15 × 10⁻³⁴ J s
h h denotes the Planck constant. J s Conditions and scope The value is expressed in joule seconds in the SI. Exact definitions do not remove uncertainty from practical measurements.
Sources · 5 Evidence and review Exact SI value, symbol, unit and defining scope.
2026-10-09 · English value and scope checked against BIPM; value compared with NIST. This review covers the definition only.
Foundational review 2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places 2026-10-10 Agreement within this scope
Planck’s constant has exact SI value 6.62607015×10−34 J s.
The national translation implements the same international defining constant.
National Metrology Institute of Japan, AIST
Related reference entries Area of Study All areas of study Mathematics & logic Physics Chemistry Biology Earth & cosmos Information Measurement Relationship group All relationships Scientific relationships Learning guidance
Explore relationships within this area of study and its connections to other areas.
Showing 1–4 of 4 relationships
Scientific relationships · 4 / 4 The relationship type describes the connection. Its linked statements, sources and conditions define the scope.
Uses definition Relationship sources · 2 The photon relation E = hf uses the Planck constant with energy and frequency in the same frame.
Uses definition Relationship sources · 2 The one-dimensional scalar-potential time-evolution equation uses ℏ = h/(2π).
Uses definition Relationship sources · 1 Linked statements
A Kibble balance combines weighing mg=I Bℓ with velocity-mode U=vBℓ to eliminate the common geometry-field factor: mgv=IU. Electrical measurements can refer to Josephson 2e/h and quantum-Hall h/e² standards, while velocity and local gravity connect to metre and second realizations. Virtual power relates mechanical measurements to h-based quantum electrical realizations with matched-mode conditions.
Uses definition Relationship sources · 1 Linked statements
For a free-particle plane-wave component in a stated frame, momentum p=ħk and nonzero momentum magnitude gives wavelength λ=h/|p|. Massive particles can show interference/diffraction; their wavefunction is not a classical material string. A localized wave packet contains a spread of momenta and does not have one exact wavelength. This relation concerns the stated de broglie wavelength and particle momentum claim and its conditions; it does not assert an unqualified prerequisite or an additional theorem.
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Record identity si-planck-constant
Revision 1
Structured reference record SI