LBS to KG Converter — Convert Pounds to Kilograms (Exact: kg = lb × 0.45359237)
High-accuracy pounds (lb) to kilograms (kg) converter using the exact international avoirdupois definition 1 lb = 0.45359237 kg. Built for fitness, shipping, nutrition, science, and manufacturing.
Exact identity: kg = lb × 0.45359237. Explore all of our free weight conversion calculators for stones, ounces, grams, and more.
About Pounds to Kilograms Conversion
Pound (lb) dominates everyday use in the United States—bathroom scales, parcel drops, and grocery labels. Kilogram (kg) is the SI base unit for mass and the lingua franca in science and global trade. Converting lb → kg accurately keeps multi-region catalogs, e-commerce feeds, shipping APIs, and fitness dashboards consistent. If your team publishes in both systems, centralize the constant and convert at the edge to avoid silent inconsistencies across pages and reports. For a broader view of mass units, visit our weight conversion hub.
LBS to KG Formula
Exact relationship
Multiply pounds by the exact SI-defined constant:
kg = lb × 0.45359237Example:
150 lb × 0.45359237 = 68.0388555 kg → 68.04 kg (2 d.p.)Reverse calculation (kg → lb)
Use the precise inverse:
lb = kg × 2.20462262185Related Weight Converters
What is a Pound (Avoirdupois)?
The international avoirdupois pound is defined as exactly 0.45359237 kilograms. It’s the standard used in retail, logistics, and consumer products across the U.S. and many legacy systems worldwide. Don’t confuse it with the troy pound used in bullion markets—those values will not match this converter.
What is a Kilogram?
The kilogram is the SI base unit for mass, defined via the Planck constant for long-term stability and international consistency. Because it harmonizes with other SI units, kg is preferred for scientific reporting, quality control, and cross-border commerce.
Step-by-Step: Converting lb to kg
- Record the mass in lb.
- Multiply by 0.45359237.
- Choose display precision for your use case (e.g., 1–2 decimals for consumer readouts).
- Label results as kg and, if needed, include both units for mixed audiences.
Walkthrough:
Gym PR: 185 lb × 0.45359237 = 83.91459 kg → 83.9 kg on the whiteboard
Parcel: 7.5 lb × 0.45359237 = 3.402 kg → 3.40 kg on the labelCommon Conversions
Everyday quick checks
| lb | kg |
|---|---|
| 1 | 0.45359 |
| 5 | 2.26796 |
| 10 | 4.53592 |
| 20 | 9.07185 |
| 50 | 22.67962 |
| 100 | 45.35924 |
| 150 | 68.03886 |
| 200 | 90.71847 |
Precision, Rounding & Significant Figures
Operational rounding
Use one decimal for fitness progress and headlines, two decimals for pricing and labels, and more for QA and research. Store raw values as exact as possible; round only once on output to maintain auditability across exports and dashboards.
Consistent documentation
Name fields clearly (e.g., mass_lb, mass_kg) and add a methods note: “Conversion uses kg = lb × 0.45359237 (exact). Inverse lb = kg × 2.20462262185.” Consistency prevents confusion when teams collaborate across regions.
Where This Converter Is Used
- 🏋️ Fitness & health: Translating gym PRs, cutting or bulking targets, and weigh-ins for international audiences.
- 📦 Shipping & logistics: Harmonizing lb-based carrier APIs with metric-based warehouse systems.
- 🥫 Food & nutrition: Converting recipes, meal prep, and nutrition panels to match consumer expectations.
- 🏭 Manufacturing & QA: Maintaining SI-compliant bills of materials while quoting in pounds for U.S. distributors.
- 🧪 Science & education: Classroom exercises and lab records that present both lb and kg for clarity.
- 🛍️ E-commerce: Product specs that switch automatically based on locale while keeping a single source of truth.
Quick Reference Table
| kg | lb |
|---|---|
| 1 | 2.20462 |
| 5 | 11.02311 |
| 10 | 22.04623 |
| 20 | 44.09245 |
| 50 | 110.23113 |
| 100 | 220.46226 |
Frequently Asked Questions
What is the exact formula to convert pounds to kilograms?
Use the international avoirdupois identity: kg = lb × 0.45359237. This constant is exact by definition (since 1959) and is used globally in science, manufacturing, and commerce. If your spreadsheet or API uses 0.45 or ‘÷ 2.2’, expect rounding drift in totals and audits.
Why should I avoid the shortcut ‘divide by 2.2’?
The 2.2 shortcut is handy for mental math, but it introduces a systematic error of roughly 0.21%. That might be harmless for casual estimates, but it can cause visible mismatches in shipping charges, nutrition labels, manufacturing tolerances, or fitness progress over time. Use 0.45359237 and round only for display.
Are troy pounds the same as the pounds used here?
No. Precious metals use the troy system, which defines mass units differently. Everyday weight—body weight, parcels, groceries—uses the international avoirdupois pound. This converter maps avoirdupois pounds to kilograms. If you’re working with bullion, use a dedicated troy converter.
How many kilograms is 150 lb? What about 10 lb?
150 lb × 0.45359237 = 68.0388555 kg (≈ 68.04 kg at 2 decimals). 10 lb × 0.45359237 = 4.5359237 kg (≈ 4.54 kg). The calculator below keeps full precision internally and shows a rounded output for convenience.
What rounding should I use for reports or product pages?
Choose a policy that matches your audience: fitness trackers and consumer copy usually show one decimal; shipping labels often use two; lab notebooks and QA records keep two to four. Store unrounded values and round once on output to avoid compounding error across transformations.
How do I convert back from kilograms to pounds?
Invert the mapping: lb = kg × 2.20462262185. In code or spreadsheets, keep constants in one place, run conversions at the boundary (ingress/egress), and avoid multi-stage conversions (lb → oz → kg) that magnify rounding.
Does ‘weight’ here mean mass or force?
In everyday settings we treat ‘weight’ as mass, so lb and kg behave as mass units. If your task involves forces (e.g., physics calculations), use newtons (N). For retail, fitness, logistics, and nutrition, lb ↔ kg is the correct pair.
How can I sanity-check my spreadsheet or ETL job quickly?
Use anchors: 1 lb → 0.45359237 kg; 100 lb → 45.359237 kg; 220.462262 lb → 100.000000 kg. If outputs don’t match before rounding, verify that 0.45359237 is used exactly and that rounding happens only at presentation time.
Tips for Working with LB & KG
- Document unit expectations near inputs (“Enter weight in lb”). Mixed-unit UIs are the #1 source of user error.
- Convert once at system boundaries; keep full precision internally; round only for the final display.
- If your audience spans the UK/Ireland, include stones/stone-pounds links to reduce confusion.
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