{"id":100143,"date":"2026-02-15T20:20:50","date_gmt":"2026-02-15T20:20:50","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100143"},"modified":"2026-07-12T16:51:38","modified_gmt":"2026-07-12T16:51:38","slug":"length-unit-converter","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/sr\/calculators\/length-unit-converter\/","title":{"rendered":"Traceable Length Unit Converter"},"content":{"rendered":"\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Traceable Length Unit Converter\",\"description\":\"Convert a curated set of SI and exact non-SI length units using rational arithmetic, source-disclosed factors and 15-significant-digit rounding.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/length-unit-converter\/\",\"applicationCategory\":\"Engineering 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class=\"vc-header\"><p class=\"vc-eyebrow\">Exact factors \u00b7 controlled display rounding<\/p><h1 class=\"vc-title\">Traceable Length Unit Converter<\/h1><p class=\"vc-sub\">Convert a curated set of SI and non-SI length units with exact rational factors. Results are rounded once to 15 significant digits; decimal point, decimal comma, signs and scientific notation are supported.<\/p><div class=\"vc-badges\"><span class=\"vc-badge\">BIPM SI Brochure 9th ed., v4.01<\/span><span class=\"vc-badge\">NIST SP 811<\/span><span class=\"vc-badge\">No binary-float conversion arithmetic<\/span><\/div><\/header>\n<div class=\"vc-card\"><form id=\"vc-form\" class=\"vc-form\" autocomplete=\"off\"><div class=\"vc-grid\"><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-value\">Value<\/label><input class=\"vc-input\" id=\"vc-value\" inputmode=\"decimal\" placeholder=\"e.g. 1.25 \/ 1,25 \/ -2e-6\"><p class=\"vc-help\">Signed quantities are allowed. Exponent range: \u22121,000,000 to +1,000,000.<\/p><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-unit\">Source unit<\/label><select class=\"vc-select\" id=\"vc-unit\"><option value=\"\">Select\u2026<\/option><option value=\"A\">\u00c5ngstr\u00f6m (\u00c5)<\/option><option value=\"nm\">Nanometre (nm)<\/option><option value=\"um\">Micrometre (\u00b5m)<\/option><option value=\"uin\">Microinch (\u00b5in)<\/option><option value=\"mil\">Mil \/ thou (mil)<\/option><option value=\"mm\">Millimetre (mm)<\/option><option value=\"cm\">Centimetre (cm)<\/option><option value=\"in\">International inch (in)<\/option><option value=\"ft\">International foot (ft)<\/option><option value=\"yd\">International yard (yd)<\/option><option value=\"m\">Metre (m)<\/option><option value=\"km\">Kilometre (km)<\/option><option value=\"mi\">International mile (mi)<\/option><option value=\"nmi\">International nautical mile<\/option><\/select><\/div><\/div><p class=\"vc-error\" id=\"vc-error\" role=\"alert\"><\/p><div class=\"vc-warning\"><strong>Quantity boundary:<\/strong> this tool converts numerical length quantities only. It does not convert nominal designations such as DN, NPS, AWG, sheet gauge or tolerance grades, and it does not infer whether a value is a magnitude, coordinate, displacement amplitude, peak, peak-to-peak or RMS.<\/div><\/form><div class=\"vc-results\" id=\"vc-results\" hidden aria-live=\"polite\"><button type=\"button\" class=\"vc-copy\" id=\"vc-copy\">Copy displayed results<\/button><div class=\"vc-rgrid\" id=\"vc-rgrid\"><\/div><p class=\"vc-note\" id=\"vc-note\"><\/p><\/div><\/div>\n<div class=\"vc-section vc-open\"><button type=\"button\" class=\"vc-toggle\" aria-expanded=\"true\">Factors, definitions and scope<\/button><div class=\"vc-body\"><div class=\"vc-inner\"><h3>Conversion model<\/h3><p class=\"vc-code\">x<sub>target<\/sub> = x<sub>source<\/sub> \u00d7 k<sub>source<\/sub> \/ k<sub>target<\/sub><\/p><p>Each k is the exact number of metres per unit shown below. Input is parsed as an integer coefficient and a power of ten. Conversion uses integer rational arithmetic; only the displayed result is rounded, to 15 significant digits using round-half-up. Scientific notation is used outside the fixed-display range. A displayed value is therefore not evidence of measurement uncertainty or significant figures.<\/p><div class=\"vc-table-wrap\"><table class=\"vc-table\"><thead><tr><th>Unit<\/th><th>Exact metres per unit k<\/th><th>Basis<\/th><\/tr><\/thead><tbody><tr><td>\u00c5<\/td><td class=\"vc-code\">10\u207b\u00b9\u2070 m<\/td><td>BIPM historical name for an SI submultiple<\/td><\/tr><tr><td>nm<\/td><td class=\"vc-code\">10\u207b\u2079 m<\/td><td>SI prefix<\/td><\/tr><tr><td>\u00b5m<\/td><td class=\"vc-code\">10\u207b\u2076 m<\/td><td>SI prefix<\/td><\/tr><tr><td>\u00b5in<\/td><td class=\"vc-code\">2.54\u00d710\u207b\u2078 m<\/td><td>10\u207b\u2076 international inch<\/td><\/tr><tr><td>mil<\/td><td class=\"vc-code\">2.54\u00d710\u207b\u2075 m<\/td><td>10\u207b\u00b3 international inch<\/td><\/tr><tr><td>mm<\/td><td class=\"vc-code\">10\u207b\u00b3 m<\/td><td>SI prefix<\/td><\/tr><tr><td>cm<\/td><td class=\"vc-code\">10\u207b\u00b2 m<\/td><td>SI prefix<\/td><\/tr><tr><td>in<\/td><td class=\"vc-code\">0.0254 m<\/td><td>International inch, exact<\/td><\/tr><tr><td>ft<\/td><td class=\"vc-code\">0.3048 m<\/td><td>International foot, exact<\/td><\/tr><tr><td>yd<\/td><td class=\"vc-code\">0.9144 m<\/td><td>International yard, exact<\/td><\/tr><tr><td>m<\/td><td class=\"vc-code\">1 m<\/td><td>SI base unit<\/td><\/tr><tr><td>km<\/td><td class=\"vc-code\">10\u00b3 m<\/td><td>SI prefix<\/td><\/tr><tr><td>mi<\/td><td class=\"vc-code\">1609.344 m<\/td><td>5280 international feet, exact<\/td><\/tr><tr><td>nautical mile<\/td><td class=\"vc-code\">1852 m<\/td><td>BIPM Table 8<\/td><\/tr><\/tbody><\/table><\/div><h3>Authoritative scope<\/h3><p>The <a href=\"https:\/\/www.bipm.org\/en\/publications\/si-brochure\/\" target=\"_blank\" rel=\"noopener\">BIPM SI Brochure, 9th edition, version 4.01, updated 2026<\/a> defines the SI and prefixes and lists 1 \u00c5 = 10\u207b\u00b9\u2070 m and 1 nautical mile = 1852 m. The <a href=\"https:\/\/www.bipm.org\/en\/si-base-units\/metre\" target=\"_blank\" rel=\"noopener\">metre definition<\/a> fixes the numerical value of the speed of light in vacuum c at 299 792 458 when expressed in m\u00b7s\u207b\u00b9; equivalently, one metre is the path travelled by light in vacuum in 1\/299 792 458 second.<\/p><p><a href=\"https:\/\/www.nist.gov\/pml\/special-publication-811\/nist-guide-si-appendix-b-conversion-factors\" target=\"_blank\" rel=\"noopener\">NIST SP 811 Appendix B<\/a> documents the international yard as exactly 0.9144 m and foot as exactly 0.3048 m; inch, mile, mil and microinch follow exactly. NIST states that the <a href=\"https:\/\/www.nist.gov\/news-events\/news\/2023\/01\/new-years-eve-2023-marked-retirement-us-survey-foot\" target=\"_blank\" rel=\"noopener\">U.S. survey foot became obsolete on 2023-01-01<\/a> except for historical and legacy applications. This converter therefore means the international foot and international mile; it does not silently process legacy survey-foot data.<\/p><h3>Why the pipe and application tables were removed<\/h3><p>DN and NPS are nominal designations, not length units. Their outside diameters depend on the governing product standard and scope. For example, <a href=\"https:\/\/www.asme.org\/getmedia\/3b3dad99-fbc1-417c-af2d-1058dfc8c55b\/b36-10_2022_toc.pdf\" target=\"_blank\" rel=\"noopener\">ASME B36.10-2022<\/a> covers welded and seamless wrought steel pipe, while other products and materials use other standards. The former unsourced \u201cDN (mm) \u2194 NPS\u201d table was therefore removed from this generic converter. Likewise, surface roughness, vibration displacement and tolerances require their quantity definition, statistic and governing standard\u2014not merely a length factor.<\/p><h3>Former defects corrected<\/h3><p>The previous page used <span class=\"vc-code\">parseFloat<\/span>, rejected decimal comma through <span class=\"vc-code\">type=number<\/span>, accepted numeric prefixes in malformed input, and rounded ordinary outputs to only two or four decimal places (for example 1 m became 39.37 in). Overflow showed unexplained dashes. Default 1000 mm, the unscoped pipe table, approximate factors presented beside exact factors, subjective claims about the metre and unsupported application ranges were removed.<\/p><\/div><\/div><\/div><footer class=\"vc-footer\">\u00a9 2024\u20132026 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u00b7 Scientific review July 2026<\/footer><\/div>\n<script>(function(){'use strict';function $(i){return document.getElementById(i)}var U={A:{n:1n,e:-10,l:'\u00c5ngstr\u00f6m (\u00c5)'},nm:{n:1n,e:-9,l:'Nanometre (nm)'},um:{n:1n,e:-6,l:'Micrometre (\u00b5m)'},uin:{n:254n,e:-10,l:'Microinch (\u00b5in)'},mil:{n:254n,e:-7,l:'Mil \/ thou (mil)'},mm:{n:1n,e:-3,l:'Millimetre (mm)'},cm:{n:1n,e:-2,l:'Centimetre (cm)'},in:{n:254n,e:-4,l:'International inch (in)'},ft:{n:3048n,e:-4,l:'International foot (ft)'},yd:{n:9144n,e:-4,l:'International yard (yd)'},m:{n:1n,e:0,l:'Metre (m)'},km:{n:1n,e:3,l:'Kilometre (km)'},mi:{n:1609344n,e:-3,l:'International mile (mi)'},nmi:{n:1852n,e:0,l:'International nautical mile'}};var ORDER=['A','nm','um','uin','mil','mm','cm','in','ft','yd','m','km','mi','nmi'];function pow10(k){return 10n**BigInt(k)}function parse(s){s=String(s).trim();if(!s||s.includes('.')&&s.includes(','))return null;var m=s.match(\/^([+-]?)(?:(\\d+)(?:[.,](\\d*))?|[.,](\\d+))(?:[eE]([+-]?\\d+))?$\/);if(!m)return null;var frac=m[3]!==undefined?m[3]:m[4]||'',whole=m[2]||'0',es=m[5]||'0';if(es.length>8)return null;var ex=Number(es);if(!Number.isInteger(ex)||Math.abs(ex)>1000000)return null;var digits=(whole+frac).replace(\/^0+\/,'')||'0',n=BigInt(digits);if(m[1]==='-')n=-n;var e=ex-frac.length;if(n===0n)return{n:0n,e:0};while(n%10n===0n){n\/=10n;e++}return{n:n,e:e}}function abs(n){return n<0n?-n:n}function flog(n,d){var a=abs(n),an=a.toString().length,ad=d.toString().length,k=an-ad;if(k>=0){if(a<d*pow10(k))k--}else if(a*pow10(-k)<d)k--;return k}function roundDiv(a,b){return(2n*a+b)\/(2n*b)}function format(n,d,e,sig){if(n===0n)return'0';var neg=n<0n,a=abs(n),kr=flog(a,d),k=kr+e,shift=e-(k-sig+1),q=shift>=0?roundDiv(a*pow10(shift),d):roundDiv(a,d*pow10(-shift)),lim=pow10(sig);if(q>=lim){q\/=10n;k++}var z=q.toString().padStart(sig,'0'),out;if(k>=sig||k<-6){out=z[0]+(z.slice(1).replace(\/0+$\/,'')?'.'+z.slice(1).replace(\/0+$\/,''):'')+'e'+(k>=0?'+':'')+k}else{var pos=k+1;if(pos<=0)out='0.'+'0'.repeat(-pos)+z;else if(pos>=sig)out=z+'0'.repeat(pos-sig);else out=z.slice(0,pos)+'.'+z.slice(pos);if(out.includes('.'))out=out.replace(\/0+$\/,'').replace(\/\\.$\/,'')}return(neg?'-':'')+out}function clear(){var g=$('vc-rgrid');g.innerHTML='';g.dataset.rows='[]';$('vc-note').textContent='';$('vc-results').classList.remove('vc-visible');$('vc-results').setAttribute('hidden','')}function fail(m){clear();$('vc-error').textContent=m}function calc(){var p=parse($('vc-value').value),u=$('vc-unit').value;if(!$('vc-value').value.trim()&&!u){$('vc-error').textContent='';clear();return}if(!p||!(u in U)){fail('Enter one complete finite decimal value and select its source unit. 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