How we verify every conversion
Every number on Panglify is computed from the official definition of its unit and checked before it goes live. Here are our sources, the exact values we use and how we test them.
Where do Panglify's conversion factors come from?
Every conversion factor on Panglify comes from the official definition of its unit, not from a rounded rule of thumb or another converter. We work from primary sources:
- the BIPM SI Brochure (9th edition), which defines the International System of Units, including the kelvin and the prefixes kilo, mega and giga;
- NIST Special Publication 811 and SP 330, and NIST Handbook 44 for US customary units;
- the 1959 International Yard and Pound Agreement, which fixed the inch at exactly 2.54 cm and the pound at exactly 0.45359237 kg;
- the UK Weights and Measures Act 1985 for imperial units such as the imperial gallon;
- IEC 80000-13 for binary data prefixes (KiB, MiB, GiB), and the W3C CSS Values and Units Module Level 3 for pixels, points and picas;
- the IANA time zone database for time zones and daylight saving rules, and European Central Bank reference rates for currencies.
Which exact definitions do the converters use?
The values below are the exact figures every Panglify tool computes with; the table is generated from the same data files that drive the calculators.
| Unit | Value used | Basis |
|---|---|---|
| 1 inch | 2.54 cm | exact, 1959 International Yard and Pound Agreement |
| 1 foot | 0.3048 m | exact, 12 inches |
| 1 mile | 1,609.344 m | exact, 5,280 feet |
| 1 nautical mile | 1,852 m | exact, international definition |
| 1 pound (avoirdupois) | 0.45359237 kg | exact, 1959 agreement |
| 1 ounce (avoirdupois) | 28.349523125 g | exact, 1/16 lb |
| 1 troy ounce | 31.1034768 g | exact, used for precious metals |
| 1 US gallon | 3.785411784 L | exact, 231 cubic inches |
| 1 imperial gallon | 4.54609 L | exact, UK Weights and Measures Act 1985 |
| 1 US fluid ounce | 29.5735295625 mL | exact, 1/128 US gallon |
| 1 US customary cup | 236.5882365 mL | exact, 8 US fl oz |
| 1 US legal cup | 240 mL | exact, FDA 21 CFR 101.9 nutrition labeling |
| 1 metric cup | 250 mL | Canada, Australia, New Zealand |
| 1 standard atmosphere | 101,325 Pa | exact, BIPM |
| 1 psi | 6,894.757293 Pa | derived from the pound-force and the inch |
| Standard gravity | 9.80665 m/s² | exact, defines the kilogram-force and pound-force |
| 1 calorie (thermochemical) | 4.184 J | exact, used on US and EU food labels |
| 1 calorie (International Table) | 4.1868 J | exact |
| 1 BTU (International Table) | 1,055.05585262 J | exact to the definition |
| 1 kilowatt-hour | 3,600,000 J | exact, 3.6 MJ |
| 1 mechanical horsepower | 745.699871582 W | derived, 550 ft·lbf/s |
| 1 metric horsepower (PS) | 735.49875 W | exact, 75 kgf·m/s |
| 1 electrical horsepower | 746 W | exact |
| 1 CSS pixel | 1/96 in | W3C CSS Values and Units Level 3 |
| 1 point | 1/72 in | DTP point, used by CSS and modern software |
| 0 °C | 273.15 K | exact, BIPM SI Brochure |
| 1 kibibyte (KiB) | 1,024 bytes | IEC 80000-13 |
How do the calculator, tables and text always agree?
They are generated from one source of truth. Each category stores its unit factors once. The live converter, the formula box, the worked examples, the conversion chart, the “Also equals” strip, the comparison table and the scale diagram on every page are all computed from those same numbers by code when the site is built, so a table can never contradict the calculator above it.
We never type a converted value by hand. When a page says 5 kilograms is 11.0231 pounds, that figure was calculated, not copied.
How precise are the results?
Calculations use full double precision, about 15 to 17 significant digits, the IEEE 754 standard every modern browser uses, and nothing is rounded until the result is shown.
- In Auto mode a result shows up to 8 significant digits; you can also choose 2 to 8 decimal places.
- Conversion charts round to 4 decimal places unless the page says otherwise.
- Conversions with an offset, such as Celsius to Fahrenheit, are rounded at 10 decimal places to remove floating-point noise such as 5.7 × 10⁻¹⁴ where the true answer is 0.
- Conversions between number bases use arbitrary-precision integers, so long binary or hexadecimal values stay exact.
Which standards can you switch between?
Where a unit has more than one legal definition, the converter lets you choose instead of silently picking one. Each switch uses the exact value of each standard:
| Switch | Options | Where |
|---|---|---|
| Gallon | US gallon (3.785411784 L) or imperial gallon (4.54609 L) | Liters to gallons |
| Fuel economy | US mpg or UK mpg | MPG to L/100km |
| Cup | US customary (236.59 mL), US legal (240 mL), metric (250 mL) or imperial (284.13 mL) | mL to cups |
| Spoons | US, metric (15 mL / 5 mL) or Australian (20 mL tablespoon) | Tablespoons to teaspoons |
| Horsepower | mechanical (745.70 W), metric PS (735.49875 W) or electrical (746 W) | HP to kW |
| Ounce | avoirdupois (28.349523125 g) or troy (31.1034768 g) | Grams to ounces |
| Calorie | thermochemical (4.184 J) or International Table (4.1868 J) | kJ to kcal |
| Data units | decimal SI (1 GB = 1,000 MB) or binary IEC (1 GiB = 1,024 MiB) | MB to GB |
| Resolution | 72, 96, 150, 300 or 600 DPI, or any custom value | Pixels to inches |
| Root font size | 10 to 20 px, or any custom value | Pixels to rem |
What about values that cannot be exact?
Some conversions depend on the real world, so we give typical values and say so plainly.
- Cooking: a cup of flour in grams depends on the flour and how it is packed. Our figures are typical spooned-and-leveled weights.
- Construction: tons per cubic yard of gravel, sand or soil vary with moisture and grading, so we show ranges and advise confirming with your supplier.
- Sizes: shoe and ring sizes follow published charts, but brands vary by up to half a size.
- Currency: rates are fetched live from European Central Bank reference data via Frankfurter each working day. We never hard-code a rate, and a conversion is a guide, not a quote or financial advice.
- Time zones: your browser applies the IANA database for the exact date you choose, so daylight saving time is handled automatically.
How is every page checked before it goes live?
Every page passes automated checks on each build, and any fact that is not a fixed definition is reviewed by a person.
- Conversion factors are taken from the primary sources above.
- Every table, example and diagram is computed by code.
- Each calculator is tested against independent reference values.
- The build checks every page for unfilled fields, duplicate questions, dead internal links and valid structured data, and it only links to pages that exist.
- Facts that are not fixed definitions (appliance wattages, typical tire pressures, paper sizes) are reviewed against published sources, and each page shows the date it was last updated.
What Panglify does not do
We explain conversions; we do not give professional advice. Electrical pages point you to your local electrical code and a licensed electrician for wiring. Currency pages are not financial advice. Advertising, if shown, never changes a result, and every calculation runs in your browser: the values you type are not sent to us.
How do I report an error?
Email hello@panglify.com or use the contact page. We check every report against the primary source, correct the page if we were wrong, and update its date. You can read more about the project on our about page.