Ounces to Kilograms Converter — Convert oz to kg (Exact: kg = (oz × 28.349523125) ÷ 1000)
Accurate ounces (oz) to kilograms (kg) converter using the exact definition 1 oz = 28.349523125 g. Includes formula, step-by-step examples, precision/rounding guidance, expanded quick tables, and rich FAQs.
Exact factor: 1 oz = 28.349523125 g ⇒ kg = (oz × 28.349523125) ÷ 1000. See all free weight metric converters.
About Ounces to Kilograms Conversion
The ounce (oz) is common in U.S. recipes, retail packs, and carrier labels, while the kilogram (kg) is the SI base unit used by global catalogs, customs, and scientific workflows. Converting ounces to kilograms lets a single dataset serve both audiences without duplication.
The constant 1 oz = 28.349523125 g is exact by international agreement. Because 1 kg = 1000 g, mapping ounces to kilograms through grams yields exact results: kg = (oz × 28.349523125) ÷ 1000. For back-of-the-envelope estimation, oz × 0.02835 is fine, but publish and compute with the exact constant in production systems and round once at output.
If your stack integrates both metric-first systems (warehouse, customs) and imperial-first systems (domestic storefronts, carriers), standardize three things: a canonical storage unit (often kg), the exact constants you use, and a single rounding policy. A short methods note prevents subtle, time-consuming discrepancies later.
Ounces to Kilograms Formula
Exact relationship
Use either expression:
kg = (oz × 28.349523125) ÷ 1000
// mental math
kg ≈ oz × 0.028349523Example:
16 oz → (16 × 28.349523125) ÷ 1000 = 0.45359237 kgRelated Weight Converters
What is an Ounce (oz)?
The ounce used here is the international avoirdupois ounce—an everyday unit of mass. It equals exactly 28.349523125 grams. Do not confuse it with the fluid ounce (fl oz), a unit of volume, or with the troy ounce (31.1034768 g) used for precious metals. Label units clearly when documentation mixes systems to prevent mistakes.
What is a Kilogram (kg)?
The kilogram is the SI base unit of mass. Since 2019, it’s defined via a fixed value of the Planck constant, ensuring long-term stability independent of physical artifacts. Because the entire SI mass family (g, mg, tonne) derives from kg, using kilograms as your canonical unit keeps analytics and interoperability predictable.
In practice, teams store kilograms for inventory and freight while rendering grams/ounces on the surface for user-friendly precision. This arrangement maintains scientific rigor while supporting day-to-day tasks.
Step-by-Step: Converting oz to kg
- Read the mass in ounces (oz).
- Multiply by 28.349523125 to get grams, then divide by 1000 to get kilograms (kg).
- Round once at presentation time per your policy (e.g., 3–4 decimals in kg for summaries; more for QA).
Example walkthrough:
Input: 2.5 oz
Compute: (2.5 × 28.349523125) ÷ 1000 = 0.07087381 kg
Output: 0.07087 kg (UI, rounded to 5 decimals)Common Conversions
Everyday quick checks (oz → kg)
| oz | kg |
|---|---|
| 1 | 0.02835 |
| 2 | 0.05670 |
| 4 | 0.11340 |
| 8 | 0.22680 |
| 12 | 0.34019 |
| 16 (1 lb) | 0.45359 |
| 32 (2 lb) | 0.90718 |
| 64 (4 lb) | 1.81437 |
| 100 | 2.83495 |
| 200 | 5.66990 |
| 500 | 14.17476 |
| 1000 | 28.34952 |
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_kg, mass_oz, mass_lb) and add a methods note: “Exact constants: 1 oz = 28.349523125 g; 1 lb = 453.59237 g. Inverse (derived): 1 kg = 35.27396195 oz.” Consistency prevents confusion when teams collaborate across regions.
Where This Converter Is Used
- 🏋️ Fitness & health: Translating gym PRs and weigh-ins for audiences that prefer ounces.
- 📦 Shipping & logistics: Harmonizing oz-based carrier labels with kg-based warehouses.
- 🥫 Food & nutrition: Converting U.S.-oriented recipes to SI-consistent data pipelines.
- 🏭 Manufacturing & QA: SI-compliant BOMs rendered in ounces for distributors.
- 🧪 Science & education: Classroom labs that present both oz and kg for clarity.
- 🛍️ E-commerce: Specs that auto-switch units by locale while keeping one source of truth.
Quick Reference Table
Common kilogram values (kg → oz)
| kg | oz |
|---|---|
| 0.10 | 3.52740 |
| 0.25 | 8.81849 |
| 0.50 | 17.63698 |
| 1.00 | 35.27396 |
| 2.00 | 70.54792 |
| 5.00 | 176.36981 |
| 10.00 | 352.73962 |
| 20.00 | 705.47924 |
Frequently Asked Questions
What is the exact formula to convert ounces to kilograms?
Use the internationally fixed constant for the avoirdupois ounce: 1 oz = 28.349523125 g (exact). Since 1 kg = 1000 g, the exact mapping is kg = (oz × 28.349523125) ÷ 1000. For mental math you might approximate kg ≈ oz × 0.02835, but in production code, specs, exports, and audits you should compute with the exact constant and round once at display.
How many kilograms is 32 oz? Show working and rounding.
Compute with kg = (oz × 28.349523125) ÷ 1000. For 32 oz: (32 × 28.349523125) ÷ 1000 = 0.90718474 kg. Displaying to 5 decimals gives 0.90718 kg. Keep full precision internally and round only at the final presentation step for alignment across PDFs, dashboards, and CSVs.
Is an ounce here mass or volume? What about fluid ounces?
This page uses the avoirdupois ounce (oz) as a unit of mass. A fluid ounce (fl oz) is a unit of volume and belongs in volume converters (e.g., fl oz ↔ mL). If a recipe lists fl oz but you need mass, you must know the ingredient density to convert volume to mass.
What precision should I use for oz → kg?
For cooking and shipping summaries, 3–4 decimals in kilograms are usually sufficient; for QA, coffee/baking, or R&D, track grams precisely internally and convert to kilograms for display. Round once at output time so the numbers in invoices, labels, and analytics match exactly.
How is this related to pounds and ounces?
There are exactly 16 ounces in 1 pound (lb). If you need lb as well, you can convert oz → kg (exact) and then kg → lb with lb = kg × 2.20462262185 (derived), or convert oz → lb directly using lb = oz ÷ 16. Keep one canonical store—typically kilograms—and compute lb/oz at the edges.
Database design: should I store kilograms, grams, or ounces?
Store a single canonical unit (commonly kilograms) and compute grams/ounces/pounds for UI and APIs. Some teams store grams to prefer integers. Whatever you choose, document it in a short methods note and apply conversions in one place with a single rounding policy.
Why do catalogs and labels mix metric and imperial units?
Global catalogs and customs tend to be metric-first (kg/g), while U.S. consumer labels and carrier APIs often use lb/oz. Converting with exact constants and rounding once keeps manifests, receipts, and customer emails numerically aligned across regions.
How do I document my conversion policy to prevent confusion?
Add a concise methods note to specs and data dictionaries: “Canonical mass unit: kg. Exact constants: 1 oz = 28.349523125 g; 1 lb = 453.59237 g. UI rounds to X decimals.” That tiny note eliminates subtle discrepancies later.
Tips for Working with Ounces & Kilograms
- Keep SI (kg) canonical; compute oz/lb at the edge for regional UX.
- Publish one rounding policy and reuse it across UI, PDFs, and exports.
- Don’t mix mass with volume: if converting mL ↔ g/oz/kg, include ingredient density and temperature conditions.