SI bestiary

This page shows inadequate, improper or bad use of metric system. Enjoy ride provided by human erroneous, ignorance and stupidity.


During metric conversion in UK, the UK Department for Transport claimed that drivers would be “confused” if metric-only signs were permitted. So how many different units are there on this congested sign?

Answer: there are no less than four different units: yards, feet, inches and metres (assuming, of course that “m” has been used correctly to denote “metres” – not “miles”!).

Credit: A very British mess. A report by the UK Metric Association, 2004, ISBN: 0750310146.

Kelvin Peta Henry

New unit appeared in USA:

(Click image for larger one.)

First one is a speed limit sign in Blaine (WA, USA), second one is speed limit sign in Point Roberts (WA, USA). These should be so called "metric" signs, with both imperial and SI units. What unit is used? Lets think: "K" stands usually for "Kelvin", "P" is "Peta", "H" is "Henry". So: "Kelvin Peta Henry". I am really curious why they need such strange unit on road sign?

Oh, maybe it should be "km/h"? It is funny how civil servants can't read simple guide how to use SI and especially correct speed unit "km/h" or "km.h-1. No capital "K", no "per", no dots to denote abbreviations.

Credit: First photo by Bourquie at en.wikipedia (CC-BY-SA-3.0), October 2010. Second photo by "Bucky".

Speed limit next 16 km

Metric and customary speed limit sign at the beginning of the exit ramp at Terminal 3 of JFK Airport (Jamaica NY, Queens):

What is the meaning of this sign? Speed limit of 10 MPH next 16 km (if Km means km). Afterwards speed is unlimited, I suppose.

Errors: the symbol for kilometers incorrectly has a capital K, and the division symbol (slash) and hour (h) are missing from the metric side.

Credit: Text by Metric signs on roads in the U.S., image provided by Tom Li, picture taken 2004 August.

Metrological audit of icebreaker Sankt Erik

The Sankt Erik is an icebreaker and a museum ship attached to the Vasa Museum in Stockholm, Sweden:

My colleges Dominik Pražák and Martin Vičar made a metrological audit of this ship and found following pressure gauges:

There are utilized 5 distinct pressure units on the ship:

Meter Vatten
kg/cm2 (kp/cm2)

And following 2 are used as second scale units:

It means to remember 10 (for some people 20) conversion factors!

Moreover unit kilograms per square centimeter has 9 symbols (omitting kp/cm2):

KG. PR. □ CM.□cm.□Ctmr.


  1. It is obvious why sailors were heavy drinkers.
  2. No instrument has a valid calibration.
  3. Swedish metrological institute neglected metrological supervision in this case.

Credit: Text and photo by my colleagues Dominik Pražák and Martin Vičar, 2007, see their original report.

Kelvin metre

Everyone knows what does unit Km mean. Of course it is the Kelvin metre. The question is, what does following road signs mean?:

The kelvin metre is probably unit of power per thermal conductivity. So this traffic signs tell us that only cars with sufficiently low ratio of power of the engine per thermal conductivity of the engine body can continue otherwise the car would overheat. Usefull when driving into hot places. Yep, seems legit. But what is Kelvin metre per hour on this traffic sign in Malta?:

Error: the symbol for kilometers incorrectly has a capital K, /h or .h-1 missing in speed unit.

Credit: First and third photo and idea by my colleague Dominik Pražák, second foto: Wikimedia Commons.

Maximal speed with distance unit

Many people know the light-year is not a time unit but a distance unit. This czech road sign was probably created with similar logic:

Error: missing /h or .h-1 after km to express unit of speed correctly.

Credit: Wikimedia Commons.

Kgs and variations

This one was hard. What is kilogram times second? You can see it on stepladders, or transport boxes:

Surprisingly, there is an interesting discussion about meaning of kg·s on My favorite explanation is the kg·s represents the lifetime of a particle. So one could say the stepladder has lifetime 150 kg·s.

Error: extra s. Kilogram is always kg, independently on plural or singular form.

Errors of "professionals"

This is a result of "professionals", Timing Solutions Ltd., under a supervision of another "professionals" Guinness World Records. There was an attempt to make a world speed record with a lawn mower, and this is an official measurement document:

(Click image for larger one.)

What is incorrect? kph, this is unfortunately common, see previous posts.
But also:

  1. Values of time measurements do not have uncertainties.
  2. There is not specified how the event (start/stop) was detected or any notion of a detector, only type of timer is present.
  3. Difference of End Time and Start Time has more digits than measured times itself.
  4. Uncertainty of the result is missing.
  5. Row of table says "Time", but there is speed in second and third column.

The article at Guinness World Records web page is also full of bad SI. Missing spaces between value and unit, incorrect rounding (116.575 to 116), crazy units (bhp), bad units (kgm). One would expect the company literally based on measurement would know how to present results.)

Credit: Timing Solutions Ltd., Guinness World Records.


Ways how to obfuscate an unit are numerous. One of them is to multiply unit by something and then divide it again. Nice example can be found on the consumption statement of LED lamp from whitenergy:

One have to say this is correct, the LED lamp has a consumption of 5 kilowatt hours in 1000 hours. But it is so easier to just write 5 W (5000/1000) and remove unnecessary hours. Strangely, it is correctly presented on other side of the box:

The problem of missing spaces between values and units is also a common one.

My favorite obfuscation unit is: Mm/ms - Megameter times milisecond.
Speed of light is 0.3 Mm/ms.

Credit: Whitenergy.

One hundred subtracted

Mugshot from Sheriff’s Office, Cullman County, Alabama, USA. One can see two height scales, inches and centimeters. Which one is which? Presuming the arrested man is of average size centimeters are on the left and inches on the right. Some clever fellow subtracted one hundred from centimeter scale. Maybe he wanted to save printer toner? Or to save space? I believe there is enough space even for numbers with three digits.

Source: Cullman County Sheriff’s Office as reported by Cullman Times.

Weather units

Today's weather:

  • temperature: 20 °
  • wind: 5 Kelvin Mega/Henry
  • humidity: 14%
  • pressure: 1023 Megabarn/second.
Temperature as angle, quite strange. Wind is maybe related to electrical units? The pressure is most interesting: weather for particle physicists!


  • temperature: 20 °C
  • wind: 5 km/h
  • humidity: 14 %
  • pressure: 1023 mbar (or 1023 hPa, or the best one 102.3 kPa)
Always put C as Celsius after degree symbol. Prefix kilo is small k (big K is Kelvin), metre is small m (big M is prefix Mega), number and percent sign should be separated by non-breaking space, b is for barn, bar is for bar. However preferred unit is Pascal!

Source: some South American TV channel. Hard to find the source, there is so many visually similar images on the internet!


I wanted to buy slippers (in Ikea). I wanted to select proper size, I picked one piece and was totally stunned. I didn't knew there si so many scales to measure slippers! Which scale is which? Is one of them centimeters? Or inches? Why Canada (or China or British Columbia) needs their own scale? Do I still live in metric country? Help!
So I used the most basic method of measurement - comparison with the standard (my own foot).

Marea transatlantic subsea cable

Take a look at the promotional picture about Marea transatlantic subsea cable Marea.

(Click image for larger one.)

Several interesting units of measurement:

  • 160 TBs/sec
  • 10,249,000 pounds
  • 6,600 km (4,000 miles)
What is 160 TBs/sec? Is it terabytes seconds per seconds? So after reduction one get 160 TB. What?
First they use pounds, than kilometers are used as primary unit. So imperials or SI? Decide!

Correctly: 160 TB/s. Bytes is never written as Bs, because s is second. The question is if author really meant TB, or TiB. I guess the second. Learn the difference!
And it is better to write everything either in SI units and imperials in brackets (preferably), or imperial units and SI in brackets. Mixing is strange.

Source: posted by Spain embassy in the USA or Microsoft on Twitter.

National Geographic Dinosaurs 101

From an educational video made by National Geographic:

Maybe a capital M and KG could be tollerated because of whole sentence in capital. Maybe.
But one cannot tollerate 99 % error in conversion from tons to kg. Another question is: which ton? British imperial or US customary? Or maybe long ton, weight ton, gross ton, short ton, net ton, ton shortweight or ton longweight?

Source: National Geography at youtube.

ULA: Launch of Atlas V USSF-7

From a live broadcast of United Launch Alliance Atlas V USSF-7 launch:

So the speed of the rocket is 9,500 kilometers that equals to 5,900 miles per hour. Distance is equal to speed? Maybe in some other universe.

One cannot simply split unit through the sentence. The 'or' seems to be redundant.
Better: 9,500 kilometers per hour or 5,900 miles per hour.
Even better: 9 500 km/h, 5 900 mph.
The best: 9 500 km/h.

By removing historical units one can get some free space that could be used to show the quantity. Like this:
Thrust: 719 kg/s
Speed: 9 500 km/s
Altitude: 112 km
Down range: 116 km

Source: United Launch Alliance at youtube.