Simetrium
A passport for every unit of measurement. In 36 languages.
Main entrance · search units, quantities and pairs
Most asked
7
base units
22
named derived units
36
languages of the canon
00 · New on the site
Fresh unit sheets
non-SI · energy in nutrition
Caloriethe unit we eatnon-SI · speed in navigation
Knota unit named after a ropenon-SI · a count of seconds
Unix time and ISO 8601 notationa limit set by the width of the machine wordnon-SI · engine power
Horsepowera unit invented by a sales departmentnon-SI · length in astronomy
Light-year, lya distance that is also a datenon-SI · length in navigation
Nautical milea minute of arc that became a numbernon-SI · length in crystallography
Angstrom, Åa ruler that fits the atomsnon-SI · distance in astronomy
Parsecdistance from an angle of one secondnon-SI · household energy
Kilowatt-houra product, not a fractionnon-SI · the natural logarithm
The neperit lost the paperwork and won the equationsnon-SI · the decimal logarithm
The belit was divided by ten straight awaynon-SI · an exact number of metres
The astronomical unitthey stopped measuring itnon-SI · the way there and back
Round-trip time and the packet intervala wider channel, the same replynon-SI · a measure of labour
The man-hour and the man-dayit adds up but does not dividenon-SI · the term of a nuclide
Half-lifehalf of them in one term
Caloriethe unit we eatnon-SI · speed in navigationKnota unit named after a ropenon-SI · a count of secondsUnix time and ISO 8601 notationa limit set by the width of the machine wordnon-SI · engine powerHorsepowera unit invented by a sales departmentnon-SI · length in astronomyLight-year, lya distance that is also a datenon-SI · length in navigationNautical milea minute of arc that became a numbernon-SI · length in crystallographyAngstrom, Åa ruler that fits the atomsnon-SI · distance in astronomyParsecdistance from an angle of one secondnon-SI · household energyKilowatt-houra product, not a fractionnon-SI · the natural logarithmThe neperit lost the paperwork and won the equationsnon-SI · the decimal logarithmThe belit was divided by ten straight awaynon-SI · an exact number of metresThe astronomical unitthey stopped measuring itnon-SI · the way there and backRound-trip time and the packet intervala wider channel, the same replynon-SI · a measure of labourThe man-hour and the man-dayit adds up but does not dividenon-SI · the term of a nuclideHalf-lifehalf of them in one term01 · Universal converter
Convert one into another
The same mechanism that sits in every unit passport, here in universal form: pick the quantity first, then the pair of units. Factors follow the SI Brochure and NIST SP 811, with no rounding in the definitions.
Quantity: length
base: metre
1 m = 3.280839895 ft (exact, by the 1959 agreement)
02 · Catalogue of quantities
Shelves of the canon
m
base
length
24 units
kg
base
mass
18 units
s
base
time
12 units
A
base
electric current
5 units
K
base
temperature
4 units
mol
base
amount of substance
3 units
cd
base
luminous intensity
4 units
N
derived
force
9 units
Pa
derived
pressure
16 units
J
derived
energy
14 units
W
derived
power
9 units
Hz
derived
frequency
6 units
V
derived
voltage
5 units
Ω
derived
resistance
4 units
C
derived
charge
4 units
T
derived
magnetic flux density
5 units
lx
derived
illuminance
3 units
Bq
derived
radioactivity
3 units
m³
non-SI
volume
26 units
m²
non-SI
area
9 units
m/s
non-SI
speed
6 units
°
non-SI
angle
7 units
bit
non-SI
data
18 units
Fderived
electrical capacitance
12 units
Sderived
electrical conductance
13 units
Wbderived
magnetic flux
12 units
Hderived
inductance
10 units
°Cderived
temperature
8 units
lmderived
luminous flux
9 units
Gyderived
absorbed dose
12 units
Svderived
equivalent dose
11 units
katderived
catalytic activity
11 units
radderived
plane angle
13 units
srderived
solid angle
11 units
l/100km
non-SI
fuel consumption
4 units
dB
non-SI
level
3 units
pud
archive
Russian measures
12 units
fur
archive
old English
9 units
erg
archive
CGS
8 units
Ci
archive
old radiology
5 units
03 · Everyday pairs
What people convert every day
km → miles
1 km = 0.621371 mi
kg → pounds
1 kg = 2.204623 lb
°C → °F
t·9/5 + 32
l/100km → mpg
235.215 / X
GB → GiB
1 GB = 0.931323 GiB
psi → bar
1 psi = 0.0689476 bar
04 · The prefix ribbon
From quetta to quecto
Q
10³⁰
quetta
R
10²⁷
ronna
Y
10²⁴
yotta
Z
10²¹
zetta
E
10¹⁸
exa
P
10¹⁵
peta
T
10¹²
tera
G
10⁹
giga
M
10⁶
mega
k
10³
kilo
h
10²
hecto
da
10¹
deca
d
10⁻¹
deci
c
10⁻²
centi
m
10⁻³
milli
µ
10⁻⁶
micro
n
10⁻⁹
nano
p
10⁻¹²
pico
f
10⁻¹⁵
femto
a
10⁻¹⁸
atto
z
10⁻²¹
zepto
y
10⁻²⁴
yocto
r
10⁻²⁷
ronto
q
10⁻³⁰
quecto
05 · The history wing
An archive of knowledge that worked
Archive · 1780–1850
Caloric
A weightless fluid present in every body and the cause of thermal phenomena. A working formalism on which steam engines and the calorie were calculated.
Archive · 1795
The metric revolution
The metre as one forty-millionth of the meridian: a measure drawn from nature rather than from a king’s body.
Reform · 2019
SI on constants
The last physical prototype went to a museum: the kilogram is now defined through the Planck constant.
Archive · before 1918
Russian measures
Sazhen, arshin, pud, zolotnik: a system abolished by decree, still alive in texts and drawings.
06 · From quantum to cosmos
navigation by orders of magnitudePick a scale — get the units that live there
One ribbon stitches the Planck length to the radius of the observable Universe. The ticks are entrances — to where ångströms live, and to where parsecs do.
10⁻³⁵
Planck length
ℓP
10⁻¹⁵
proton
fm
10⁻¹⁰
atom
Å
10⁻⁶
cell
µm
10⁻³
grain of sand
mm
10⁰
human
m
10³
city
km
10¹¹
Earth orbit
au
10²⁶
observable Universe
Gpc
07 · Your language
Read this in your own language
EN
English
RU
Русский
DE
Deutsch
FR
Français
ES
Español
PT
Português
IT
Italiano
NL
Nederlands
PL
Polski
SV
Svenska
DA
Dansk
FI
Suomi
NB
Norsk
CS
Čeština
SK
Slovenčina
RO
Română
EL
Ελληνικά
HU
Magyar
TR
Türkçe
AR
العربية
FA
فارسی
ZH
中文（简）
ZH-HANT
中文（繁）
JA
日本語
KO
한국어
TH
ไทย
VI
Tiếng Việt
HI
हिन्दी
BN
বাংলা
ID
Indonesia
MS
Melayu
TA
தமிழ்
LA
Latina
SR
Srpski
UR
اردو
SW
Kiswahili