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 · an exact number of metresauThe astronomical unitthey stopped measuring itnon-SI · the way there and backRTTRound-trip time and the packet intervala wider channel, the same replynon-SI · a measure of labourman·hThe man-hour and the man-dayit adds up but does not dividenon-SI · the term of a nuclideT½Half-lifehalf of them in one termnon-SI · the clock and the machine cycleCLKThe processor clock and the machine cyclefrequency is no measure of worknon-SI · a count of daysJDJulian datethe day begins at noon, without breaksnon-SI · three time scalesUTCTime scales and the leap seconda second inserted by decisionnon-SI · a scale of must density°OeDegree Oechslehow much extra a litre of juice weighsnon-SI · a conventional scale°ZInternational Sugar Scalesugar as light sees itnon-SI · volume fraction% volAlcoholic strengththree scales of one strengthnon-SI · a count of secondsunixUnix time and ISO 8601 notationa limit set by the width of the machine wordnon-SI · conventional viscosity°EEngler degreean instrument that is its own standardnon-SI · density of liquids°APIHydrometer degreesa scale turned upside down against densitynon-SI · plane angle°Degree of arc360 has exactly 24 divisorsleveldBDecibelhow many times over, not how much
01 · 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
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