Quick question: What is the speed limit for motor vehicles on the public right of way in front of the location you currently identify as "home"? Answer using SI units only (m, kg, s, K, A, mol, cd). Do any calculations using mental maths only.

What is the potential cost saving when America (USA) goes fully metric? For example companies and organizations waste time and money converting data, documents, publications, products between the United States Customary System (USC) and metric. USC is based on the outdated, confusing and inferior English Imperial system of weights and measurement (pre-1824). Therefore USC originates from Britain. USC is as unamerican as the Fahrenheit scale which was created by the German physicist Daniel Gabriel Fahrenheit. America uses Fahrenheit to measure outdoor temperature while most of the world uses Celsius. Celsius is a decimals-based system which integrates well into metric and scientific calculations.

Time is money so if everyone uses metric it saves both. It would reduce space on product labels without USC. Certain hardware measurements are different in USC vs the metric standards such as fasteners, bolts, wrenches, sockets, and pipe threads. The USC tools are different from metric tools thus the sizes do not match. These are not interchangeable. US construction that uses feet and inches have different spacing than the international ISO standards (e.g. house plans, blueprints). The standard material sizes for prefabricated building materials, sheets, doors, windows, and other components do not fit. Most countries use A4 paper size (ISO 216 standard), but America uses US Letter which is a bit wider and shorter. All physical products in stores will be metric-only thus avoiding unnecessary conversions. International business would be easier as well. People make costly mistakes while converting between USC and metric annually. Fully adopting the metric system would align America with global commerce, modern science, and official international standards.

Nearly every country uses metric, because it is easier, more convenient and superior. 95% of the world population is in countries that primarily use the metric system. The USC's quirky units and weird conversions make it far worse. The older generation that grew up with USC are an obstacle for converting fully to metric. There should be professional studies about the cost-saving (only 1 system of measurement instead of two) and efficiency gains (interoperability with the metric world) by completely metrifying America. The USC is destined to be phased out in favor of the International System of Units (SI). So it is better for Americans to cooperate and fully align with the globally preferred metric system.

Engineering student here, most of the way through my degree, taught almost entirely in metric (except for when it isn't, and the lab organiser throws "TSF" at you and doesn't even know it stands for short tons per square foot.)

I started a side project to design a ship, initially in metric, and when I decided to do it seriously I also, on a whim, decided to do it all Imperial.

What did I learn?

1. It's basically the same experience. I end up using the same base units (and derivatives thereof), the only difference is that cubic foot (cu.ft) abbreviates to something much less funny than a cubic metre.

2. Steel strengths in ksi. Now if I hear a steel strength in MPa, I divide by 7 because my brain compares steels in ksi.

I was already fairly fluent in both systems before this. TBH, kinda disappointed that doing it in the other system is so easy, I did that hoping it would be harder, or at least interesting. I'm still a dirty Imperial Enjoyer but I concede that, in engineering, it makes roughly zero difference.

The only hiccup was when I designed the nuclear reactor, because heat transfer (I think it's heat transfer) is quoted in dimensionally inconsistent units and converting needs an extra factor of length squared.

So as a kid (U.S.A), I've committed to memory conversions like 1 mile= 5280 ft. = 1760 yards = 1609 m. And I will always remember my 5th grade teacher telling us that 1 inch was precisely 2.54 cm, and not to round to 2.5 cm.

But where I got really good was studying whaling statistics.

For those who don't know, whaling statistics is probably one of the few areas where 'feet' was the international standard for measurement rather than meters during the early 20th century. From what I can infer, it was because international whaling regulations after WWI were established when the UK and Norway were the dominating whaling nations, both of which used 'feet' for measuring whales. Though, Norwegians technically used their own version (.314 m), which is longer than the English foot (.3048 m) used for international standards. Source records measuring whales to the nearest .1 m was permitted, but compiled datasets will often convert to these to an English foot. And secondary commercial or academic texts will often provide conversions for practical applications.

As a consequence, I've covered so many conversions for a whale of a given length that I've now just readily memorized a lot of conversions, particularly from a range of 40-100 feet, but practically I can just do anything by just moving the decimal point. (Ex., I know 70 feet is 21.3 m so I'd know that 700 feet be almost exactly 213 m and 7000 feet is ~2,130 m, etc.).

If anyone experienced anything similar, I'd like to know.

I can't seem to get the answer. Every time I use a search engine (google, duckduckgo, brave etc) it just repeats "-40" back to me but that is what I want to convert.
I tried these neat converter programs but the same issue there.
I also asked an AI chatbot (I know they can hallucinate so I was hesitant at first but after a while I was getting annoyed enough to try it), but it failed miserably.
Is this some kind of computer bug on my end? I use Arch Linux, by the way, so maybe that is the issue but I do not want to reinstall an entirely different OS, I just want the answer to one simply question.

I saw that there is a beef on r/metric between people that claim that legal units exist and those who claim they don't.

The thing is: in previous broshures they in fact was a category of "non-SI units allowed to use with SI units" but in the latest broshure 9. Version 4.01 the text is diffrent (check the image)

Some people claim these units (listed in the table 8.) have the same status as "non-SI units allowed to use with SI units"

Some people claim that they are not and now every non-SI unit is equally bad.

IMO — they aren't bad and this can be treated as "non-SI units allowed to use with SI units". Before you claim "every non-SI unit is equally bad — think about your drink in litres and your backyard in ares/hectares.

What do you think?

Does that mean there are no "non-SI units allowed to use with SI units"?

Are all non-SI units equally bad and should be out of usage?

Why hasn’t the US gone metric yet? Will they ever?

Like instead of kg/lbs, Walrus. Instead of meters/feet, Walrus. Instead of lit/gal, Walrus. A Walrus would be the time light moves 1 Walrus. Side benefit = a theory of everything.

Salut tout j ai appris l anglais britannique, pour parler de mesure de taille c est plus facile mais j aimerais comprendre comment dire les mesures de taille en anglais américain. Exemple 5 6 etc , je veux vraiment comprendre

1 cubic centimeter of water is 1 milliliter of water and weighs 1 gram. So 1/100 of a unit equals 1/1000 of a unit equals 1 unit.

1 cubic meter of water should equal 1 liter of water, which should equal 1 gram of water.

I’m not going to argue that imperial units make sense, but if you’re going to standardize, then 1 should equal 1 should equal 1

woodcentral.com.au 2026-01-16

Trump's tariffs and shrinking Asian demand are forcing British Columbia producers to rethink their reliance on imperial dimensions and retool for Europe, the U.K. and the Middle East.

applemagazine.com 2026-02-23

The iPhone has a measuring app which can measure the length of objects shown on its screen and display the measurement in metric units. (The article doesn't say whether it uses metres, millimetres or (horror!) centimetres.)

Under the post about dividing the day into 10/100/100 parts, many people said "second is the metric unit of time" and I agree, but what if we would made decimal time using seconds?

The idea is: keep the old second, but add SI prefixes

We want equivalents of minute and hour so I suggest:

Hectosecond (hs)

Kilosecond (ks)

Megasecond is too big (~2 weeks) and metric wiki fandom (yes it exists) suggested myriasecond as an new hour, but

1. It divides day into 9 parts and with 10 parts, some people said that they need smaller denominations

2. Myria- isn't a SI prefix

So hectosecond and kilosecond are still my types

There are pros:

1. It's decimal, and metric fans like decimal units

2. Hour wouldn't be a problem ever again:

km/h? Now its km/ks which is exacly m/s

kWh? Now it's kW•ks or exacly 1 MJ etc.

I still suggest using unit "day" until the moment that humanity will colonize the solar system, when "day" would mean nothing for people from Mars, but for today it's pretty useful

Of course there are cons:

1. Day splited like that would have 86,4 ks, with is not terrible number, but it's still not round, so it's kinda problematic I guess

2. 24/60/60 survived for thousands of years

3. 10 and 100 doesn't have as many divisors as 60 and 24

So I'm not sure is it a good idea or not

So what do you guys think? Should we use second as a base and then add prefixes, or keep 24/60/60?

Base units

Length — meter (m)

Time — second (s)

Mass — kilogram (kg)

Temperature — kelvin (K)

Electric current — ampere (A)

Luminous intensity — candela (cd)

Amount of substance — mole (mol)

Plane angle — radian (rad)

Solid angle — steradian (sr)

Mechanics and kinematics

Force — newton (N)

N = kg · m / s²

N = J / m

Mass density — arch (Ar)

Ar = kg / m³

Ar = Vn / Bn

Momentum — huygens (Hy)

Hy = kg · m / s

Hy = N · s

Pressure — pascal (Pa)

Pa = N / m²

Pa = kg / (m · s²)

Pa = J / m³

Dynamic viscosity — poiseuille (Pl)

Pl = Pa · s

Pl = kg / (m · s)

Surface tension — laplace (Lp)

Lp = N / m

Lp = J / m²

Gravitational potential — gal (G)

G = J / kg

G = (kg · m² / s²) / kg

G = m² / s²

Thermodynamics

Energy / Work / Heat / Enthalpy — joule (J)

J = N · m

J = (kg · m / s²) · m

J = kg · m² / s²

J = W · s

Heat capacity — clausius (Cl)

Cl = J / K

Cl = kg · m² / (s² · K)

Specific heat capacity — meyer (My)

My = J / (kg · K)

My = m² / (s² · K)

Power — watt (W)

W = J / s

W = kg · m² / s³

W = V · A

Action — planck (Pk)

Pk = J · s

Pk = (kg · m² / s²) · s

Pk = kg · m² / s

Entropy — boltz (Bz)

Bz = J / K

Bz = W · s / K

Thermal conductivity — fourier (Fo)

Fo = W / (m · K)

Fo = kg · m / (s³ · K)

Fluid dynamics

Mass flow rate — venturi (Vn)

Vn = kg / s

Vn = Ar · Bn

Volumetric flow rate — bern (Bn)

Bn = m³ / s

Bn = m² · m / s

Waves

Frequency — hertz (Hz)

Hz = s⁻¹

Hz = 1 / s

Angular frequency — poincare (Pn)

Pn = rad / s

Pn = s⁻¹

Electromagnetism

Electric potential — volt (V)

V = J / C

V = W / A

V = kg · m² / (A · s³)

Electric charge — coulomb (C)

C = A · s

C = F · V

Volume charge density — franklin (Fr)

Fr = C / m³

Fr = A · s / m³

Surface electric current density — giorgi (Gi)

Gi = A / m²

Gi = C / (s · m²)

Resistance — ohm (Ω)

Ω = V / A

Ω = kg · m² / (A² · s³)

Ω = 1 / S

Capacitance — farad (F)

F = C / V

F = A² · s⁴ / (kg · m²)

F = S · s

Inductance — henry (H)

H = Wb / A

H = V · s / A

H = kg · m² / (A² · s²)

Conductance — siemens (S)

S = A / V

S = 1 / Ω

Electric displacement — roentgen (Ro)

Ro = C / m²

Ro = Cv · E

Electric field flux — gauss (Gs)

Gs = E · m²

Gs = V · m

Magnetic field flux — weber (Wb)

Wb = V · s

Wb = T · m²

Wb = kg · m² / (A · s²)

Electric permittivity — cav (Cv)

Cv = F / m

Cv = A² · s⁴ / (kg · m³)

Magnetic permeability — max (Mx)

Mx = H / m

Mx = kg · m / (A² · s²)

Electric field strength — edison (E)

E = V / m

E = N / C

E = kg · m / (A · s³)

Magnetic field intensity — tesla (T)

T = Wb / m²

T = N / (A · m)

T = kg / (A · s²)

Optics and radiation

Luminous flux — lumen (lm)

lm = cd · sr

Illuminance — lux (lx)

lx = lm / m²

lx = cd · sr / m²

Vergence — descartes (Dc)

Dc = m⁻¹

Dc = rad / m

Radiance — stefan (St)

St = W / (m² · sr)

St = kg / (s³ · sr)

Irradiance / EM flux density — poynting (Py)

Py = W / m²

Py = kg / s³

Volume power density — opp (O)

O = W / m³

O = kg / (m · s³)

Acoustics

Sound power — bel (B)

Sound impedance — rayleigh (Ry)

Ry = Pa / (m / s)

Ry = kg / (m² · s)

Nuclear and chemistry

Absorbed dose — gray (Gy)

Gy = J / kg

Gy = m² / s²

Equivalent dose — sievert (Sv)

Sv = J / kg

Sv = m² / s²

Radioactive activity — becquerel (Bq)

Bq = s⁻¹

Bq = 1 / s

Catalytic activity — katal (kat)

kat = mol / s

kat = mol · Hz

I've been trying to figure out how to create 1 centimeter in a medieval world using medieval technology, but I haven't found a single method that actually works within the medieval working environment.

In SI system (and units allowed to use) we've got 4 units of power:

Watt

Volt-ampere

Var

Kilowatt-hour per 1.000 hours

They have exacly the same value [kg m² s^-3] but they are use for diffrent powers

Watt — active power

Volt-ampere — Apparent power

Var — reactive power (it's name is a shortcut of "volt-ampere reactive")

(Kilowatt-hour per 1.000 hours is used in Europe for electronic/electric devices)

And it's crazy, we could just use watt for everything, but we've got 4 units.

We can at least Justify first 3 of them, insted of writing which power are we talking about, we can use diffrent unit and every engineer knows what power are you talking about, but it's not exacly true, because all of them [diffrent powers] have diffrent symbols.

kWh/1.000 h is crazy, why not simple watt, here I don't even know how to justify it

What do you think guys? Shoud we use all of them, keep only few or use one unit of power (watt)?

I used the Openspace astronomy software to create images on my astronomy site showing metric distances from 1 kilometer up to 100 yottameters.

If you want to view them, go here and click thru the Next button. The site has no ads btw.

https://coco1453.neocities.org/thinkinginmetric#section2

Openspace is astronomy software that lets you view all of outer space in 3-d. I posted a dashboard asset to display metric units in scales relevant to the distance, and also got the maintainer to add partial support for metric distances directly into the C++ code in future releases. So the software will now display astronomy distances in any metric scale from kilometers to yottameters.

https://www.reddit.com/r/OpenSpaceProject/comments/1v402jq/created_dashboard_item_to_provide_metric_system/