Converters

Units / Radix / Timestamp · 8 tools

Unit conversion is a place where a wrong constant stays wrong silently. Every factor here comes from the defining standard rather than from a rounded table: the inch is exactly 25.4 mm by definition, the pound is exactly 453.59237 g, the nautical mile is exactly 1852 m, and the international acre is exactly 4046.8564224 m².

Two things trip people up more than the arithmetic. Areas and volumes scale with the square and cube of the linear factor, so 1 ft² is not 0.3048 m² but 0.09290304 m². And storage has two parallel scales — decimal (1000, what drive vendors print) and binary (1024, what operating systems report) — which is the entire reason a "1 TB" drive shows up as 931 GiB.

Which one do I need?

Engineering or shipping dimensions: length. Feet, inches, yards and miles are exact multiples of the metre-based definitions, so no precision is lost by converting.
Sizing a disk, a bucket or a transfer: data size. Check which scale the answer is in — TiB and TB differ by about 9 percent, and GB versus GiB by the same order.
Estimating storage cost or bandwidth: the same tool, read in the other direction. 100 Mbps of network throughput is 12.5 MB/s, because a byte is eight bits.
Regional units: 斤 (jin), 斤 (taijin, Taiwan) and 司马斤 (Hong Kong) are all different weights, as are 亩 and 坪 for area. They are listed explicitly so the distinction is visible rather than assumed.
Timestamps and bases: the Unix timestamp converter treats values of 1e12 and above as milliseconds — a heuristic, not a rule. The base converter uses BigInt, so it handles values past 2^53 - 1 where ordinary JavaScript arithmetic would round them.

All tools in this category

Length Unit ConverterHOT Convert instantly between metric and imperial length units: mm, cm, m, km, inch, foot, yard, mile, nautical mile. Weight / Mass Converter Convert between milligram, gram, kilogram, ton, ounce, pound, jin and liang. Area Unit Converter Convert between square meter, square kilometer, hectare, mu, square foot and square mile. Volume Unit Converter Convert between milliliter, liter, cubic meter, US gallon, UK gallon and cubic foot. Storage Capacity Converter Convert between bit, B, KB, MB, GB, TB, PB, showing both 1000 (decimal) and 1024 (binary) results. Speed Unit Converter Convert instantly between m/s, km/h, mph, knot and ft/s. Base / Radix Converter Convert between 2/8/10/16 and any 2–36 bases, with BigInt for large numbers and grouped binary output. Unix Timestamp ConverterHOT Convert timestamps to dates and back, auto-detecting seconds/ms, with UTC and local time zone toggle.

Guides in this category

FAQ

Why does my 1 TB drive show 931 GiB?

Drive vendors use decimal prefixes: 1 TB means 1,000,000,000,000 bytes. Operating systems historically report binary units: 1 GiB means 1,073,741,824 bytes. Divide one by the other and you get about 0.9313, so the same physical capacity appears to shrink by roughly 6.9 percent. Nothing is missing — the label and the report use different prefixes.

Why do timestamps need separate seconds and milliseconds handling?

Unix time is defined in seconds, but JavaScript, Java and many APIs use milliseconds. The two differ by a factor of 1000, and a value interpreted in the wrong unit lands decades away from the intended date. The 1e12 threshold used here separates the two ranges for modern dates, but millisecond timestamps from 1970 to 2001 fall below it and will be misread as seconds.

Does Unix time account for leap seconds?

No. Unix time counts 86,400 seconds per day and ignores leap seconds entirely, so it drifts about one second behind UTC over a few years and is periodically corrected by a jump. For scheduling and logging that is irrelevant; for astronomical or high-precision timing it is not.