How do you use this tool?
- Enter a weight in stone (whole stones or decimal stones) to get the equivalent in kilograms.
- Or enter kilograms to get the stone and pounds breakdown.
- The result shows both decimal kilograms and the stone + remaining pounds format (e.g., 11 st 4 lbs).
- Use the copy button to grab the converted value.
What This Tool Does
The Stone to Kilograms Converter translates body weight measurements between stone (the UK unit), kilograms (the metric unit), and pounds (the US unit) — showing all three so you have a complete picture regardless of which system you’re working in. It also outputs the mixed stone-plus-pounds format (e.g., 11 st 4 lbs) used in everyday British and Irish speech.
How It Works
The chain of exact definitions:
| Conversion | Exact value |
|---|---|
| 1 stone → pounds | 14 lbs (exact, by definition) |
| 1 pound → kilograms | 0.45359237 kg (exact, international pound) |
| 1 stone → kilograms | 6.35029318 kg |
Conversion reference table:
| Stone | Kilograms | Pounds |
|---|---|---|
| 7 st | 44.45 kg | 98 lbs |
| 8 st | 50.80 kg | 112 lbs |
| 9 st | 57.15 kg | 126 lbs |
| 10 st | 63.50 kg | 140 lbs |
| 11 st | 69.85 kg | 154 lbs |
| 12 st | 76.20 kg | 168 lbs |
| 13 st | 82.55 kg | 182 lbs |
| 14 st | 88.90 kg | 196 lbs |
| 15 st | 95.25 kg | 210 lbs |
| 20 st | 127.01 kg | 280 lbs |
| 25 st | 158.76 kg | 350 lbs |
Mixed format breakdown: To convert decimal stone to stone + pounds, take the whole number of stones and multiply the decimal remainder by 14. Example: 11.5 st = 11 st + (0.5 × 14) lbs = 11 st 7 lbs = 73.03 kg.
What Are Common Use Cases?
Following British TV and media — The stone unit appears constantly in UK health, fitness, and lifestyle content that American audiences watch. Understanding that a contestant weighing “12 stone 4” on a British show means 172 lbs or 78.0 kg makes the content more accessible.
Communicating with UK family or colleagues — Americans with British or Irish relatives often receive health updates in stone. Converting to pounds or kilograms makes the information meaningful in a US context.
Boxing and combat sports — British boxing promotions use stone for weight classes. Matchroom Boxing and Eddie Hearn regularly publish weights in stone; US fans can convert to the familiar pound or kilogram class names.
Historical research and British literature — British novels, medical records, and historical documents from the 19th and 20th centuries record weights in stone. Converting allows comparison with modern BMI and weight data.
UK fitness apps and programs — Apps like Noom UK edition, British fitness YouTubers, and NHS-linked weight loss programs (designed for UK audiences) display weight in stone. American users who download or follow these programs need to convert to understand their progress benchmarks.
Online shopping for UK-designed clothing — Some UK brands size clothing by stone-based weight ranges. Understanding the stone scale helps when reading size guides from ASOS, Marks & Spencer, or other UK retailers shipping to the US.
Frequently Asked Questions
Why does the UK use stone when the rest of the world uses kilograms? The stone is a traditional British imperial unit that was never replaced during metrication for the specific context of body weight. The UK officially adopted metric in 1995 for most trade, but body weight remains culturally attached to stone — similar to how the US has retained Fahrenheit for everyday temperatures while using Celsius in science.
What is a “stone” in historical context? Historically, a “stone” was a physical stone of standardized weight used as a trade measure, varying by region and commodity (a stone of wool was 14 lbs in England; in Scotland it could be different). The current 14-pound definition was standardized by the UK Weights and Measures Act of 1835.
How does stone relate to the BMI scale? UK BMI calculators and NHS weight guidance frequently express the healthy weight range in stone. For a 5’10” (178 cm) person, the healthy BMI range (18.5–24.9) corresponds to roughly 9 st 3 lbs to 12 st 6 lbs (58.5–79.0 kg). This converter lets you map your own measurements against those ranges quickly.
Last updated: