About

Percentage computation across heterogeneous units is error-prone. Converting 326.25 m against 5 km requires correct normalization to a common base before division. Mixing up 1024-based file size units with 1000-based prefixes produces silently wrong results in storage capacity reports. This tool normalizes six distinct domains - raw numbers, dates, time durations, file sizes, lengths, and mass - to their canonical base units before applying the ratio formula vT × 100. All conversion factors follow SI definitions and common conventions: file sizes use binary prefixes (1 KB = 1024 B), lengths use the international yard-pound agreement (1 yd = 0.9144 m), and months approximate to 30.4167 days from 36512.

Limitation: date calculations assume Gregorian calendar and do not account for leap-second corrections. Time duration tokens use fixed averages for months and years. The tool truncates results to the specified decimal places without banker's rounding. For financial or scientific reporting requiring IEEE 754 compliance, verify edge cases independently.

Formulas

The core operation across all six modes reduces to a single ratio scaled to 100:

P = VT × 100

Where P = percentage result, V = the value (numerator) normalized to base units, and T = the total (denominator) normalized to the same base units. The result is truncated to d decimal places where d defaults to 2.

For the Dates mode, the formula expands to a positional interpolation:

P = t_target − t_startt_end − t_start × 100

Where t_target, t_start, and t_end are Unix epoch timestamps in milliseconds obtained from JavaScript Date.parse.

For Time durations, the parser tokenizes input strings using the pattern: [value][unit] repeated (e.g., 3h2min30sec) or the colon-separated format HH:MM:SS.ms. Each token is multiplied by its millisecond factor and summed.

For Filesize, binary prefixes are used: 1 KB = 1024¹ B, 1 MB = 1024² B, and so on through YB at 1024⁸.

Reference Data

Domain	Unit	Symbol	Base Unit	Conversion Factor
Filesize	Byte	B	B	1
Filesize	Kilobyte	KB	B	1024
Filesize	Megabyte	MB	B	1,048,576
Filesize	Gigabyte	GB	B	1,073,741,824
Filesize	Terabyte	TB	B	1.0995 × 10¹²
Filesize	Petabyte	PB	B	1.1259 × 10¹⁵
Filesize	Exabyte	EB	B	1.1529 × 10¹⁸
Filesize	Zettabyte	ZB	B	1.1806 × 10²¹
Filesize	Yottabyte	YB	B	1.2089 × 10²⁴
Length	Millimeter	mm	m	0.001
Length	Centimeter	cm	m	0.01
Length	Decimeter	dm	m	0.1
Length	Meter	m	m	1
Length	Kilometer	km	m	1000
Length	Foot	ft	m	0.3048
Length	Inch	in	m	0.0254
Length	Yard	yd	m	0.9144
Mass	Milligram	mg	g	0.001
Mass	Gram	g	g	1
Mass	Kilogram	kg	g	1000
Mass	Pound	lb	g	453.592
Mass	Ounce	oz	g	28.3495
Time	Millisecond	ms	ms	1
Time	Second	sec	ms	1,000
Time	Minute	min	ms	60,000
Time	Hour	h	ms	3,600,000
Time	Day	d	ms	86,400,000
Time	Week	w	ms	604,800,000
Time	Month	m	ms	2,628,000,000
Time	Year	y	ms	31,536,000,000

Frequently Asked Questions

This tool follows the convention used in the percentage-js specification: 1 year = 365 days and 1 month = 36512 ≈ 30.4167 days. For astronomical or financial year calculations requiring 365.25 or 360-day conventions, adjust your input accordingly.

Binary prefixes are used throughout: 1 KB = 1024 B, 1 MB = 1,048,576 B. This matches how operating systems report storage. If your data uses SI decimal prefixes (kB = 1000 B), convert to bytes first and use the Numbers mode.

Division by zero is caught and returns an error toast. The result displays "undefined" since V0 is mathematically undefined. Ensure T ≠ 0 for valid output.

Dates are parsed via the browser's native Date constructor, which interprets strings in the local time zone unless an explicit offset is provided (e.g., 2024-06-15T12:00:00Z). DST transitions may cause a ±1 hour discrepancy. For cross-timezone precision, append UTC offsets to your date strings.

Yes. If V > T in numeric, filesize, length, or mass modes, the result exceeds 100%. In date mode, if the target date falls before the start date, the result is negative, indicating the target precedes the range. These are mathematically valid outputs.

The colon format expects HH:MM:SS.ms. Partial inputs like 5:30 are interpreted as 5 hours and 30 minutes. A single number like 120 without colons or unit tokens is treated as 120 hours (the largest non-token unit). Always specify units explicitly if ambiguity is possible.