Internet Assigned Numbers Authority

Sensor Measurement Lists (SenML)

Last Updated
Available Formats



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Registries included below

SenML Units

Registration Procedure(s)
Expert Review
Ari Keränen
Units marked with an asterisk are NOT RECOMMENDED to be 
produced by new implementations but are in active use and 
SHOULD be implemented by consumers that can use the 
corresponding SenML units that are closer to the unscaled SI
Available Formats

Symbol Description Type Reference
m meter float [RFC8428]
kg kilogram float [RFC8428]
g gram* float [RFC8428]
s second float [RFC8428]
A ampere float [RFC8428]
K kelvin float [RFC8428]
cd candela float [RFC8428]
mol mole float [RFC8428]
Hz hertz float [RFC8428]
rad radian float [RFC8428]
sr steradian float [RFC8428]
N newton float [RFC8428]
Pa pascal float [RFC8428]
J joule float [RFC8428]
W watt float [RFC8428]
C coulomb float [RFC8428]
V volt float [RFC8428]
F farad float [RFC8428]
Ohm ohm float [RFC8428]
S siemens float [RFC8428]
Wb weber float [RFC8428]
T tesla float [RFC8428]
H henry float [RFC8428]
Cel degrees Celsius float [RFC8428]
lm lumen float [RFC8428]
lx lux float [RFC8428]
Bq becquerel float [RFC8428]
Gy gray float [RFC8428]
Sv sievert float [RFC8428]
kat katal float [RFC8428]
m2 square meter (area) float [RFC8428]
m3 cubic meter (volume) float [RFC8428]
l liter (volume)* float [RFC8428]
m/s meter per second (velocity) float [RFC8428]
m/s2 meter per square second (acceleration) float [RFC8428]
m3/s cubic meter per second (flow rate) float [RFC8428]
l/s liter per second (flow rate)* float [RFC8428]
W/m2 watt per square meter (irradiance) float [RFC8428]
cd/m2 candela per square meter (luminance) float [RFC8428]
bit bit (information content) float [RFC8428]
bit/s bit per second (data rate) float [RFC8428]
lat degrees latitude[1] float [RFC8428]
lon degrees longitude[1] float [RFC8428]
pH pH value (acidity; logarithmic quantity) float [RFC8428]
dB decibel (logarithmic quantity) float [RFC8428]
dBW decibel relative to 1 W (power level) float [RFC8428]
Bspl bel (sound pressure level; logarithmic quantity)* float [RFC8428]
count 1 (counter value) float [RFC8428]
/ 1 (ratio e.g., value of a switch; [2]) float [RFC8428]
% 1 (ratio e.g., value of a switch; [2])* float [RFC8428]
%RH Percentage (Relative Humidity) float [RFC8428]
%EL Percentage (remaining battery energy level) float [RFC8428]
EL seconds (remaining battery energy level) float [RFC8428]
1/s 1 per second (event rate) float [RFC8428]
1/min 1 per minute (event rate, "rpm")* float [RFC8428]
beat/min 1 per minute (heart rate in beats per minute)* float [RFC8428]
beats 1 (Cumulative number of heart beats)* float [RFC8428]
S/m Siemens per meter (conductivity) float [RFC8428]
B Byte (information content) float [RFC8798]
VA volt-ampere (Apparent Power) float [RFC8798]
VAs volt-ampere second (Apparent Energy) float [RFC8798]
var volt-ampere reactive (Reactive Power) float [RFC8798]
vars volt-ampere-reactive second (Reactive Energy) float [RFC8798]
J/m joule per meter (Energy per distance) float [RFC8798]
kg/m3 kilogram per cubic meter (mass density, mass concentration) float [RFC8798]
deg degree (angle)* float [RFC8798]
NTU Nephelometric Turbidity Unit float [ISO 7027-1:2016]

SenML Labels

Registration Procedure(s)
Expert Review
Ari Keränen
Available Formats

Name Label CBOR Label JSON Type XML Type EXI ID Reference Note
Base Name bn -2 String string a [RFC8428]
Base Time bt -3 Number double a [RFC8428]
Base Unit bu -4 String string a [RFC8428]
Base Value bv -5 Number double a [RFC8428]
Base Sum bs -6 Number double a [RFC8428]
Base Version bver -1 Number int a [RFC8428]
Name n 0 String string a [RFC8428]
Unit u 1 String string a [RFC8428]
Value v 2 Number double a [RFC8428]
String Value vs 3 String string a [RFC8428]
Boolean Value vb 4 Boolean boolean a [RFC8428]
Data Value vd 8 String (*) string (*) a [RFC8428] (*) Data Value is a base64-encoded string with the URL-safe alphabet as defined in Section 5 of [RFC4648], with padding omitted. (In CBOR, the octets in the Data Value are encoded using a definite-length byte string, major type 2.)
Sum s 5 Number double a [RFC8428]
Time t 6 Number double a [RFC8428]
Update Time ut 7 Number double a [RFC8428]
LwM2M Object Link vlo String string [OMA-TS-LightweightM2M_Core-V1_1_1-20190617-A] Section 7.4.5 of the OMA LwM2M 1.1 Core Technical Specification
Base Content-Format bct String string [RFC9193]
Content-Format ct String string [RFC9193]

Secondary Units

Registration Procedure(s)
Expert Review
Ari Keränen
Available Formats

Secondary Unit Description SenML Unit Scale Offset Reference
ms millisecond s 1/1000 0 [RFC8798]
min minute s 60 0 [RFC8798]
h hour s 3600 0 [RFC8798]
MHz megahertz Hz 1000000 0 [RFC8798]
kW kilowatt W 1000 0 [RFC8798]
kVA kilovolt-ampere VA 1000 0 [RFC8798]
kvar kilovar var 1000 0 [RFC8798]
Ah ampere-hour C 3600 0 [RFC8798]
Wh watt-hour J 3600 0 [RFC8798]
kWh kilowatt-hour J 3600000 0 [RFC8798]
varh var-hour vars 3600 0 [RFC8798]
kvarh kilovar-hour vars 3600000 0 [RFC8798]
kVAh kilovolt-ampere-hour VAs 3600000 0 [RFC8798]
Wh/km watt-hour per kilometer J/m 3.6 0 [RFC8798]
KiB kibibyte B 1024 0 [RFC8798]
GB gigabyte B 1e9 0 [RFC8798]
Mbit/s megabit per second bit/s 1000000 0 [RFC8798]
B/s byte per second bit/s 8 0 [RFC8798]
MB/s megabyte per second bit/s 8000000 0 [RFC8798]
mV millivolt V 1/1000 0 [RFC8798]
mA milliampere A 1/1000 0 [RFC8798]
dBm decibel (milliwatt) dBW 1 -30 [RFC8798]
ug/m3 microgram per cubic meter kg/m3 1e-9 0 [RFC8798]
mm/h millimeter per hour m/s 1/3600000 0 [RFC8798]
m/h meter per hour m/s 1/3600 0 [RFC8798]
ppm parts per million / 1e-6 0 [RFC8798]
/100 percent[3] / 1/100 0 [RFC8798]
/1000 permille / 1/1000 0 [RFC8798]
hPa hectopascal Pa 100 0 [RFC8798]
mm millimeter m 1/1000 0 [RFC8798]
cm centimeter m 1/100 0 [RFC8798]
km kilometer m 1000 0 [RFC8798]
km/h kilometer per hour m/s 1/3.6 0 [RFC8798]
ppb parts per billion / 1e-9 0 [CoRE-1]
ppt parts per trillion / 1e-12 0 [CoRE-1]
VAh volt-ampere-hour VAs 3600 0 [CoRE-1]
mg/l milligram per liter kg/m3 1/1000 0 [CoRE-1]
ug/l microgram per liter kg/m3 1e-6 0 [CoRE-1]
g/l gram per liter kg/m3 1 0 [CoRE-1]

SenML Features

Registration Procedure(s)
Specification Required
Ari Keränen (primary), Carsten Bormann (secondary)
Available Formats

Feature Code Feature Name Reference
0 Reserved0 [RFC9100]
1 Reserved1 [RFC9100]
2 Reserved2 [RFC9100]
3 Reserved3 [RFC9100]
4 Secondary Units [RFC9100][RFC8798]
5-52 Unassigned


Assumed to be in World Geodetic System 1984 (WGS84),
unless another reference frame is known for the sensor.
A value of 0.0 indicates the switch is off, 1.0 indicates
on, and 0.5 indicates half on. The preferred name of this unit is
"/". For historical reasons, the name "%" is also provided for
the same unit, but note that while that name strongly suggests a
percentage (0..100), it is NOT a percentage but the absolute
This registration does not use the obvious name "%" because 
this name has been taken in [RFC8428] already, where it is a 
NOT RECOMMENDED synonym for "/" (unity) for legacy reasons. 
Note that the presence of both "%" and "/100" with different 
meanings is likely to create confusion, so 
[RFC8798] adds some weight 
to the recommendation against using the counterintuitive unit 
name "%".