The kilogram, the base unit of mass in the International System of Units (SI), has a fascinating history tied to a physical artifact. Until 2019, it was defined by Le Grand K, a platinum-iridium cylinder stored in a vault in France. However, even slight surface contamination or material wear could alter its mass. To ensure a more stable and universally consistent measure, the kilogram is now defined by the Planck constant—a fundamental constant of nature—using a Kibble balance. This revolutionary change marked a significant milestone in metrology and brings mass measurement into line with other SI units that are already defined by fundamental constants, rather than physical objects.
The stone is a unit of weight that has a particularly rich history, mainly used in the UK and Ireland for human body weight measurement. Originating from the Biblical days, a stone was once standardized by the British Act of Parliament in 1835 to equal 14 pounds. This peculiar unit is still popular in daily life, especially in conversations about body weight or livestock; any Harry Potter fan will recognize Hagrid’s impressive weight mentioned in stones!
An interesting fact is that the symbol for stone “st” doesn’t change forms, much like “lb” for pounds, which can be confusing at first glance. Unlike metric units with their straightforward conversions, the cultural and historical essence of the stone makes it an intriguing part of British heritage, fostering a sense of continuity from medieval markets to modern times.
| Kilograms | Stones |
|---|---|
0
kg
|
0
st
|
1
kg
|
0.157473
st
|
2
kg
|
0.314946
st
|
3
kg
|
0.472419
st
|
4
kg
|
0.629892
st
|
5
kg
|
0.787365
st
|
6
kg
|
0.944838
st
|
7
kg
|
1.10231
st
|
8
kg
|
1.25978
st
|
9
kg
|
1.41726
st
|
10
kg
|
1.57473
st
|
11
kg
|
1.7322
st
|
12
kg
|
1.88968
st
|
13
kg
|
2.04715
st
|
14
kg
|
2.20462
st
|
15
kg
|
2.3621
st
|
16
kg
|
2.51957
st
|
17
kg
|
2.67704
st
|
18
kg
|
2.83451
st
|
19
kg
|
2.99199
st
|
20
kg
|
3.14946
st
|
21
kg
|
3.30693
st
|
22
kg
|
3.46441
st
|
23
kg
|
3.62188
st
|
24
kg
|
3.77935
st
|
25
kg
|
3.93683
st
|
26
kg
|
4.0943
st
|
27
kg
|
4.25177
st
|
28
kg
|
4.40925
st
|
29
kg
|
4.56672
st
|
30
kg
|
4.72419
st
|
31
kg
|
4.88166
st
|
32
kg
|
5.03914
st
|
33
kg
|
5.19661
st
|
34
kg
|
5.35408
st
|
35
kg
|
5.51156
st
|
36
kg
|
5.66903
st
|
37
kg
|
5.8265
st
|
38
kg
|
5.98398
st
|
39
kg
|
6.14145
st
|
40
kg
|
6.29892
st
|
41
kg
|
6.45639
st
|
42
kg
|
6.61387
st
|
43
kg
|
6.77134
st
|
44
kg
|
6.92881
st
|
45
kg
|
7.08629
st
|
46
kg
|
7.24376
st
|
47
kg
|
7.40123
st
|
48
kg
|
7.55871
st
|
49
kg
|
7.71618
st
|
50
kg
|
7.87365
st
|
51
kg
|
8.03113
st
|
52
kg
|
8.1886
st
|
53
kg
|
8.34607
st
|
54
kg
|
8.50354
st
|
55
kg
|
8.66102
st
|
56
kg
|
8.81849
st
|
57
kg
|
8.97596
st
|
58
kg
|
9.13344
st
|
59
kg
|
9.29091
st
|
60
kg
|
9.44838
st
|
61
kg
|
9.60586
st
|
62
kg
|
9.76333
st
|
63
kg
|
9.9208
st
|
64
kg
|
10.07827
st
|
65
kg
|
10.23575
st
|
66
kg
|
10.39322
st
|
67
kg
|
10.55069
st
|
68
kg
|
10.70817
st
|
69
kg
|
10.86564
st
|
70
kg
|
11.02311
st
|
71
kg
|
11.18059
st
|
72
kg
|
11.33806
st
|
73
kg
|
11.49553
st
|
74
kg
|
11.65301
st
|
75
kg
|
11.81048
st
|
76
kg
|
11.96795
st
|
77
kg
|
12.12542
st
|
78
kg
|
12.2829
st
|
79
kg
|
12.44037
st
|
80
kg
|
12.59784
st
|
81
kg
|
12.75532
st
|
82
kg
|
12.91279
st
|
83
kg
|
13.07026
st
|
84
kg
|
13.22774
st
|
85
kg
|
13.38521
st
|
86
kg
|
13.54268
st
|
87
kg
|
13.70015
st
|
88
kg
|
13.85763
st
|
89
kg
|
14.0151
st
|
90
kg
|
14.17257
st
|
91
kg
|
14.33005
st
|
92
kg
|
14.48752
st
|
93
kg
|
14.64499
st
|
94
kg
|
14.80247
st
|
95
kg
|
14.95994
st
|
96
kg
|
15.11741
st
|
97
kg
|
15.27489
st
|
98
kg
|
15.43236
st
|
99
kg
|
15.58983
st
|
100
kg
|
15.7473
st
|
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