Convert Pounds to Kilograms – Weight Converter
This converter converts a single numeric weight in pounds (lb) to kilograms (kg) using the internationally agreed fixed relationship between the avoirdupois pound and the kilogram. It is intended for general-purpose use such as fitness tracking, shipping estimates, and everyday unit conversion.
Results are produced using the exact international definition of the pound in terms of the kilogram and are suitable for informational and documentation purposes. For regulated or safety-critical contexts (for example clinical dosing, legal weights, or calibrated mass measurements), use calibrated instruments and follow traceability and accreditation requirements described in the references below.
Governance
Record bef96c52662e • Reviewed by Fidamen Standards Committee
Interactive Converter
Convert between pound and kilogram with precision rounding.
Quick reference table
| Pound | Kilogram |
|---|---|
| 1 lb | 0.4536 kg |
| 5 lb | 2.268 kg |
| 10 lb | 4.5359 kg |
| 25 lb | 11.3398 kg |
| 50 lb | 22.6796 kg |
| 100 lb | 45.3592 kg |
Methodology
The converter uses a single fixed multiplication factor that links the avoirdupois pound to the SI base unit kilogram. This is a deterministic, lossless arithmetic conversion before rounding.
Displayed results are formatted to a reasonable number of decimal places by default but may be rounded to fewer digits depending on context; rounding and display do not change the underlying exact relationship.
Numerical representation follows standard floating-point arithmetic practices; small rounding differences may appear when showing many decimal places. For high-accuracy applications, follow instrument calibration and measurement uncertainty procedures in ISO/IEC 17025 and traceability guidance from national metrology institutes.
Worked examples
150 lb = 150 × 0.45359237 = 68.0388555 kg → typically shown as 68.04 kg (rounded to 2 dp).
0.5 lb = 0.5 × 0.45359237 = 0.226796185 kg → typically shown as 0.2268 kg (rounded to 4 dp for small masses).
200 lb = 90.718474 kg → typically shown as 90.72 kg (rounded to 2 dp).
F.A.Q.
Is the conversion factor exact?
Yes. The international avoirdupois pound has been defined to equal exactly 0.45359237 kilograms. The multiplier used by this tool is exact by definition; displayed values are rounded for readability.
Why do I sometimes see different rounded results?
Different displays use different rounding rules and numbers of decimal places. The underlying conversion is exact; variations come from formatting (how many decimal places are shown) and floating-point representation when many decimals are requested.
Can I use results from this converter for medical dosing or regulated reporting?
This converter provides informational unit conversion only. For medical dosing, patient weight must be measured on a calibrated, traceable scale and documented per local clinical protocols. Calibration and measurement uncertainty must comply with applicable standards and facility procedures.
What does 'traceable' and 'calibrated' mean for weight measurements?
Traceability means the scale's calibration can be linked to national measurement standards through an unbroken chain of calibrations. Calibration and testing laboratories commonly follow ISO/IEC 17025. Always verify calibration certificates and intervals for regulated use.
Do you support stones and pounds input?
This converter accepts a single pounds value as input. If you have stones and pounds, convert the stones to pounds (1 stone = 14 pounds) then use this tool or use a combined converter that accepts stones and pounds.
How many decimal places should I use?
Choose decimals based on context: 1–2 decimals for shipping and fitness, 2–4 decimals for small masses or lab use, and follow institutional requirements for clinical or scientific reporting. Always document the rounding rule and consider measurement uncertainty where relevant.
Sources & citations
- NIST — SI Units and guidance on unit definitions — https://www.nist.gov/pml/si-units
- BIPM — International System of Units (SI) and base unit definitions — https://www.bipm.org/en/measurement-units
- ISO — ISO 80000 Quantities and units (overview) — https://www.iso.org/standard/67142.html
- ISO/IEC 17025 — General requirements for the competence of testing and calibration laboratories — https://www.iso.org/standard/66912.html
- IEEE — IEEE 754 standard for floating-point arithmetic (numeric representation guidance) — https://standards.ieee.org/standard/754-2019.html
- OSHA — Occupational safety and health guidance and workplace measurement considerations — https://www.osha.gov
- BIPM SI Brochure (9th edition, 2019) — https://www.bipm.org/en/publications/si-brochure
- NIST SP 811 — Guide for the Use of the International System of Units — https://www.nist.gov/pml/special-publication-811
Further resources
Related tools
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: bef96c52662eWhat changed (latest)
v1.0.0 • 2025-11-16 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-16 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Engine
v1.0.0
Data
Baseline (no external datasets)
Content
v1.0.0
UI
v1.0.0
Governance
Last updated: Nov 16, 2025
Reviewed by: Fidamen Standards Committee (Review board)
Credentials: Internal QA
Risk level: low
Reviewer profile (entity)
Fidamen Standards Committee
Review board
Internal QA
Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person
Semantic versioning
- MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
- MINOR: New features or fields that do not change existing outputs for the same inputs.
- PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.
Review protocol
- Verify formulas and unit definitions against primary standards or datasets.
- Run golden-case regression suite and edge-case suite.
- Record reviewer sign-off with credentials and scope.
- Document assumptions, limitations, and jurisdiction applicability.
Assumptions & limitations
- Uses exact unit definitions from the Fidamen conversion library.
- Internal calculations use double precision; display rounding follows the unit's configured decimal places.
- Not a substitute for calibrated instruments in regulated contexts.
- Jurisdiction-specific rules may require official guidance.
Change log
v1.0.0 • 2025-11-16 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 8e9cc4968df1
- https://standards.ieee.org/standard/754-2019.html
- https://www.bipm.org/en/measurement-units
- https://www.bipm.org/en/publications/si-brochure
- https://www.iso.org/standard/66912.html
- https://www.iso.org/standard/67142.html
- https://www.nist.gov/pml/si-units
- https://www.nist.gov/pml/special-publication-811
- https://www.osha.gov