# |
Allocation: Country (year) |
Last known location (institution, city) |
Last known status |
Last known Calibration |
Drift (µg/yr) |
Notes |
𝕶 | BIPM (1883)[6] | BIPM vault, Saint-Cloud, France | International Prototype Kilogram (IPK) "Le Grand K (𝕶)"[6] |
2014[10] | −0.50 | Drift ≈ −0.50 μg/yr over ~100 yr relative to official copies; ~+50 μg total divergence; stored under triple bell jars.[11][12][13] |
KI |
BIPM (1889)[6] |
BIPM vault, Saint‑Cloud, France |
Check standard |
2014[10] |
|
First of three nearly identical cylinders of Pt10Ir alloy fabricated in 1879.[6] |
KII |
|
Paris Observatory, Paris[6] |
|
1880[6] |
|
Compared to Kilogram of the Archives w/KI & KIII (later 𝕶) by four observers in 1880 at the Paris Observatory.[6] |
1 | France (1889) | BIPM vault, Saint‑Cloud, France | Retired check standard1889-1925 (“sister” copy).[14] |
1988-92[14] | | Retired in 1925 after falling. Replaced as an official copy by No. 7.[14] |
2 | Romania (1889) | National repository, Romania | National prototype |
2023 No. 165[15] | | |
3 | Spain (1889)[8] | National repository, Spain | National prototype |
2013 No. 48[15] | | |
4 | United States
(1889)[8] |
NIST, United States | National prototype[16] |
2013 No. 47[17] | −0.37 | 1889: -75 μg; 1989: -106 μg; ~1999: -116 μg. Net change −41 μg over ~110 yr.[18] |
5 | Italy (1889)[8] | National repository, Italy | National prototype |
1988-92[14] | | |
6 | Japan (1889)[8] | National Metrology Institute, Japan | National prototype |
1988-92[14] | | |
7 | France | BIPM vault, Saint‑Cloud, France | Official copy since 1925[10] (“sister” copy) |
1988-92[14] | | |
8 | France | BIPM vault, Saint‑Cloud, France | Official copy since 1905[10] (serial 8(41)) |
1988-92[14] | | Sister copy of IPK #8 mis‑stamped as 41[Note 2] |
9 | BIPM (1889)[8] | BIPM calibration laboratory, Saint‑Cloud, France | Working copy 2014[10] |
2014[10] | | Fell in Bunge balance 1949.[14] Used for BIPM 1963–64 verification.[19] |
10 | Portugal (1889)[8] | IPQ, Caparica | National prototype |
2022 No. 110[15] | | |
11 | Serbia (1889)[8] | National repository, Serbia | National prototype retired. |
| | Damaged 1907; 1925 replaced by No. 29.[14] |
12 | Russia (1889)[8] | VNIIM, Saint Petersburg, Russia | National prototype[20] |
2014 No. 24[15] | | |
13 | France (1889)[8] | | |
| | |
14 | Austria (1889)[8] | BEV | National prototype |
2019 No. 46[15] | | |
15 | Bavaria (1889)[8] | | |
1954[21] | | |
16 | Hungary (1889)[8] | National repository, Hungary | National prototype |
2018 No. 39[15] | | |
17 | France (1889)[8] | LNE-CETIAT | National prototype |
2015 No. 18[15] | | |
18 | United Kingdom
(1889)[8] |
National Physical Laboratory, United Kingdom | National prototype[22] |
2024 No. 11 | | |
19 | Italy (1889)[8] | | |
1954[21] | | |
20 | United States
(1889)[8] |
NIST, United States | National prototype[16] |
2019 No. 44[15] | 0.00 | 1889: -39 μg; 1948: -19 μg; 1989: -39 μg (no net drift over ~100 yr).[18] |
21 | Mexico | National repository, Mexico | National prototype |
2021 No. 107[15] | | |
22 | Germany (1889)[8] | | |
1903[23] | | Damaged in Berlin in 1944[14] |
23 | Finland | National repository, Finland | National prototype |
2022 No. 108[15] | | |
24 | Spain (1889)[8] | National repository, Spain | National prototype |
2015 No. 121[15] | | |
25 | Paris Observatory (1889)[8] |
BIPM calibration laboratory, Saint‑Cloud | Working copy (special use)[19] | 2014[10] | |
Re‑assigned 1958, to the BIPM in nearly unused condition.[19] |
26 | Saint Petersburg Academy of Sci.
(1889)[8] |
VNIIM, Saint Petersburg, Russia | Official copy[20] |
| | |
27 | Denmark (1889)[8] | | |
| | Retired 1946; 1949 replaced by No. 48,[14] |
28 | Belgium (1889)[8] | National repository, Belgium | National prototype |
2021 No. 16[15] | | |
29 | Conservatoire national des arts et métiers | National repository, Serbia | National prototype |
| | 1925 transferred from Conservatoire national des arts et métiers to Kingdom of Yugoslavia to replace No. 11.[14] |
30 | Argentina | National repository, Argentina | National prototype |
2019 No. 6[15] | | |
31 | BIPM (1889)[8] | BIPM calibration laboratory, Saint‑Cloud, France | Working copy |
2014[10] | | Fell in Bunge balance 1951.[14] Used for BIPM 1963–64 verification[19] |
32 | France | BIPM vault, Saint‑Cloud, France | Official copy since 1905[10] (“sister” copy) |
2014[10] | 0.00 | BIPM cleaning trials (2014) on Nos. 7 and 32 showed < 0.5 μg mass loss on a third full cleaning; high short‑term stability.[10][24] |
33 | Austria (1889)[8] | | |
| | |
34 | France (1889)[8] | French Academy of Sciences, Paris, France[15] | Held by non‑national organisation[17] |
2015 No. 67[15] | | |
35 | France (1889)[8] | National repository, France | National prototype |
2015 No. 74[15] | | |
36 | Norway (1889)[8] | National repository, Norway | National prototype |
2024 No. 104[15] | | |
37 | Belgium (1889)[8] | National repository, Belgium | National prototype |
2022 No. 112[15] | | |
38 | Switzerland (1889)[8] |
National repository, Switzerland | National prototype |
2015 No. 20[15] | | |
39 | Japan | National repository, South Korea | National prototype |
1988-92[14] | −6.47 | −665 μg by the 3rd PV with poor surface condition.[14] Ceded to the Republic of Korea in 1958.[11] |
40 | Sweden (1889)[8] | RISE, Borås | National prototype |
1991 No. 22[25] | -0.02 | 1889: -0.037; 1948: -0.039, 1991: -0.035(2) mg[25] |
41 | Czechoslovakia[26](1929)[14] |
Slovak Republic | |
1954 | |
Shown in 1st PV unassigned,[23] 2nd PV assigned to CS, but not in 3rd.[14] No 8(41) appears separately.[26] [Note 2] |
42′ | France | BIPM, Saint‑Cloud, France | Underweight “standard” (working copy)[Note 3][10] |
2014[10] | | Allocated to Turkey in 1935; 1953 exchanged for No 54.[14] |
43 | France | BIPM, Saint‑Cloud, France | Official copy since 1939[10] (“sister” copy)[27] |
1988-92[14] | | Used for BIPM 1963–64 verification[19] |
44 | Australia (1947)[14] | NMI, Australia | National prototype[11][17] |
2015 No. 70[15] | | Returned for BIPM 1963–64 verification on request[19] |
45 |
Argentina[19] (1939)[14] |
|
|
|
|
Not returned for BIPM 1963–64 verification on request[19] Lost 1986.[14] |
46 | Dutch East Indies
(1939)[14] |
SNSU‑BSN, Indonesia | National prototype[11][17] |
2015 No. 82[15] | | Returned for BIPM 1963–64 verification on request[19] |
47 | France | BIPM, Saint‑Cloud, France | Official copy since 1939[10] (“sister” copy)[27] |
2014[10] | | Used for BIPM 1963–64 verification[19] |
48 | Denmark (1949)[14] | DFM, Denmark | National prototype[11][17] |
2021 No. 106[15] | +0.78 | Delivered in 1949 at +81 μg; certified +112 μg in the 1988–1992 periodic verification (+31 μg over ~40 yr).[11][28][12] |
49 | Austria | BEV, Austria | National prototype[11][17] |
2019 No. 46[15] | | Returned for BIPM 1963–64 verification on request[19] |
50 | Canada | NRC, Canada | National prototype[11][17] |
1988-92[14] | | Returned for BIPM 1963–64 verification on request[19] |
51 | Poland | GUM, Poland | National prototype[11][17] |
2021 No. 4[15] | | |
52 | Germany | PTB, Germany | National prototype[11][17] |
2010 No. 21[17] | | |
53 | Netherlands | VSL, Netherlands | National prototype[11][17] |
2024 No. 12 | | 1889: Kingdom of the Netherlands had ratified but didn't adhere to the Meter Treaty and was not entitled to an original prototype.[8] |
54 | Turkey (1953)[14] | UME, Turkey | National prototype[11][17][29] |
2017 No. 48[15] | | Exchanged to replace No 42.[14] |
55 | Germany (1954)[30] |
PTB, Germany | National prototype[11][17] |
2023 No. 80[15] | +1.26 | ~126 μg/century relative to the IPK since 1954; cited as a high‑drift case.[31][32][12] |
56 | South Africa
(1955) |
NMISA, South Africa | National prototype[11][17] |
2015 No. 77[15] | | |
57 | India (1958)[33] | NPLI, New Delhi | National prototype[11][17] |
2022 No. 109[15] | | Excluded from 3rd PV cleaning mass change calculations.[14] |
58 | United Arab Republic[19] (1963)[14] | NIS, Egypt | National prototype[11][17] |
2022 No. 115[15] | | Used for BIPM 1963–64 verification[19] |
59 |
n/a |
National Research Laboratory of Metrology (Japan) |
Standard E59 |
|
|
Mistakenly listed as platinum-iridium prototype; NUM number E59.[14] |
60 | China (1963)[14] | NIM, China | National prototype[11][17] |
2023 No. 164[15] | | |
61 |
China (1963)[14] |
|
|
|
|
Retired 1978; replaced by No. 64.[14] |
62 | Istituto di Metrologia G. Colonnetti (1964)[14] | INRiM, Turin | Held by non‑national organisation[11][17] |
1988-92[14] | | |
63 | France | BIPM, Saint‑Cloud, France | Working copy[10] |
2014[10] | 0.00 | ~2 μg stability across repeated cleanings using the NBS‑2 balance.[10][24] |
64 | China | NIM, China | National prototype[11][17] |
2024 No. 103 | | |
65 | Slovakia | SMU, Slovakia | National prototype[11][17] |
2019 No. 47[15] | | |
66 | Brazil | INMETRO, Brazil | National prototype[11][17] |
2019 No. 3[15] | | |
67 | Czech Republic | CMI, Czech Republic | National prototype[11][17] |
2021 No. 2[15] | | |
68 | Chile | CENAMET, Chile | National prototype[11][17] |
1988-92[14] | | |
69 | Portugal | Portuguese Institute for Quality, Portugal | National prototype[11][17] |
2022 No. 111[15] | | |
70 | Germany | PTB, Germany | National prototype[11][17] |
2013 No. 70[17] | | |
71 | Israel (1992)[14] | INMI, Israel | National prototype[11][17] |
2015 No. 83[15] | | Newly machined, finished and adjusted @BIPM w/diamond tool.[14] |
72 | South Korea
(1992)[14] |
KRISS, South Korea | National prototype[11][17] |
2017 No. 45[15] | | Newly machined, finished and adjusted @BIPM w/diamond tool.[14] |
73 | BIPM (1988)[14] | BIPM, Saint‑Cloud, France | Special‑use working copy[10] |
2014[10] | | |
74 | Canada (1992)[14] | NRC, Canada | National prototype[11][17] |
2015 No. 23[15] | | Newly machined, finished and adjusted @BIPM w/diamond tool.[14] |
75 | Hong Kong
(1993)[34] |
SCL, Hong Kong[17] | National prototype |
2017 No. 1[15] | | Newly machined, finished and adjusted @BIPM w/diamond tool.[14] |
76 | Istituto di metrologia G. Colonnetti (1993) | INRiM, Turin | National prototype[11][17] |
2025 No. 126 | | |
77 | France (1992)[14] | BIPM, Saint‑Cloud, France | Underweight “standard”[Note 3][10] |
2014[10] | | Underweight standard; not included in drift calculations.[11][28] |
78 | Taiwan | Center for Measurement Standards (CMS), ITRI, Hsinchu[35] | National prototype[11][17] |
2025 No. 40 | | |
79 | United States
(1996)[36] |
NIST, United States | National prototype[11][17] |
2012 No. 4[17] | | |
80 | Thailand | NIMT, Thailand | National prototype[11][17] |
2023 No. 84[15] | | |
81 | United Kingdom | NPL, United Kingdom | National prototype[11][17] |
2013 No. 47[17] | | |
82 | United Kingdom | NPL, United Kingdom | National prototype[11][17] |
2004 No. 20[17] | | |
83 | Singapore | NMC, Singapore | National prototype[11][17] |
2023 No. 75[15] | | |
84 | South Korea | KRISS, South Korea | National prototype[11][17] |
2003 No. 53[17] | | |
85 | United States | NIST,[37] United States | National prototype[11][17] |
2012 No. 30[17] | | Used in 2019-20 CCM key comparison |
86 | Sweden (2002)[25] | RISE, Borås | National prototype[11][17] |
2004 No. 68[25] | | |
87 | Australia | NMI, Australia | National prototype[11][17] |
2004 No. 77[17] | | |
88 | France | BIPM, Saint‑Cloud, France | Working copy[10] |
2014[10] | | |
89 | Switzerland | METAS, Switzerland | National prototype[11][17] |
2015 No. 73[15] | | |
90 | Mexico | CENAM, Mexico | National prototype[11][17] |
2021 No. 108[15] | | |
91 | France | BIPM, Saint‑Cloud, France | Working copy[10] |
2014[10] | | |
92 | United States | NIST, United States | National prototype[11][17] |
2016 No. 134[15] | | |
93 | Saudi Arabia | SASO, Riyadh | National prototype[11][17] |
2024 No. 13[15] | | |
94 | Japan | NMIJ,[37] Tsukuba, Japan | National prototype[11][17] |
2015 No. 25[15] | | Used in 2019-20 CCM key comparison |
95 | Kenya | KEBS, Kenya | National prototype[11][17] |
2022 No. 133[15] | | |
96 | Mexico | CENAM, Mexico | National prototype[11][17] |
2021 No. 108[15] | | |
97 | | | |
| | |
98 | | | |
| | |
99 | | | |
| | |
100 | | | |
| | |
101 | | | |
| | |
102 | USA | NIST, USA[17] | |
2014 No. 53[15] | | |
103 | | | |
| | |
104 | USA | NIST, USA[37] | |
2014 No. 54[15] | | Used in 2019-20 CCM key comparison |
105 | USA | NIST, USA[17] | |
2014 No. 55[15] | | |
106 | Canada | NRC, Canada[37] | |
2015 No. 17[15] | | Used in 2019-20 CCM key comparison |
107 | Pakistan[15] | | |
2017 No. 47[15] | | |
108 | Colombia[15] | | |
2015 No. 127[15] | | |
109 | Germany | PTB, Germany[37] | |
2015 No. 5[15] | | Used in 2019-20 CCM key comparison |
110 | China | NIM, China[37] | |
2016 No. 74[15] | | Used in 2019-20 CCM key comparison |
111 | South Korea | KRISS, South Korea[37] | |
2017 No. 46[15] | | Used in 2019-20 CCM key comparison |
112 | Indonesia | SNSU‑BSN, Indonesia | |
2019 No. 98[15] | | |
113 | | | |
| | |
114 | China (2022)[38] | NIM, China | |
2022 No. 23[15] | | |
115 | China (2022) | NIM, China | |
2022 No. 36[15] | | |
650 |
BIPM |
|
Working copy since 1993[10] |
2014[10] |
|
|