Methodology & sources
Unitversal uses official reference factors, not values approximated from memory.
Length, weight, and volume units
Based on the International System of Units (SI) and conversion factors published by the BIPM (International Bureau of Weights and Measures). Example: 1 inch = 2.54 cm exactly (1959 international agreement).
Densities (cooking conversions)
Densities used for gram-to-milliliter conversions come from standard food reference tables (including Ciqual) and apply at roughly 20 °C. Real-world values can vary slightly by product.
Accuracy over time
This page is updated whenever an underlying factor changes. For safety-critical or professional use, we recommend checking the value against a calibrated reference.
Currency rates
Live rates come from the European Central Bank, which publishes one reference rate per currency around 16:00 CET on TARGET working days. There is no rate on Saturdays, Sundays or TARGET holidays: on those days the site shows the last published reference and names its date, which is why a Sunday carries Friday's figure.
Every figure is served with the date it refers to. Past four days without a new publication, the site shows no figure at all rather than an old one.
A reference rate is not the rate you will get. Banks, card networks and exchange offices add a margin, commonly 1 to 3 percent, and sometimes a fixed fee on top. Use these numbers to know what a sum is worth, not to predict what you will be charged.
The pre-euro currencies are a different matter. Their rates were not market prices but conversion rates fixed once and for all by Council Regulation (EC) No 2866/98 and its successors: 1 EUR = 6.55957 FRF is exact and definitive, in the same way that one inch is 25.4 millimeters.
Data units
Decimal definitions from IEC standard 80000-13: the kilobyte is 10³ bytes, the megabyte 10⁶, the gigabyte 10⁹. The binary prefixes kibi, mebi and gibi, which are powers of 1024, carry their own symbols Ki, Mi and Gi. A drive sold as 1 TB really does hold 10¹² bytes; if it shows 931 GB, that is the system dividing by 2⁴⁰ while keeping the decimal label.
Public sources
- BIPM, brochure du SI Definitions of the base units and of the units accepted for use with the SI.
- NIST, Special Publication 811 Guide for the use of the SI, with exact conversion factors to customary units.
- ANSES, table Ciqual Food densities used by the cooking conversions.