Imperial/US engineering units.

[eclecticfluff]

Problem you'd like to fix

A significant number of problems I've had to solve for mechanics related work has involved units that are hard or impossible to enter accurately with the supported units, let alone read an answer in the desired conversion.

Describe the solution you'd like

I would like the following list of units to be included, roughly in order of importance.

• pounds force (lbf), pound mass should be renamed to lbm.
• slug (slug)
• degree Rankine (°R)
• inches of water (inH2O), ideally would accept all length units.
• inches of mercury (inHg), ideally would accept all length units.
• thermochemical calorie (cal or calth), see #1987.
• thermochemical kilocalorie (Cal, Calth, kcal, or kcalth)
• thermochemical British thermal unit (btu or btuth)
• pounds per square inch (psi)
• kilopounds force (kip)
• kilopounds per square inch (ksi)
• poundal (pdl), unlikely to see use.

Describe alternatives you've considered

Pounds force can be input as lb g0, but it's clunky, especially when used in more complex derived units.

Additional context

The conversions can be found at the NIST table for it, though do note that some are not listed as exact conversions where exact conversions do exist.

[eclecticfluff]

Update to say that my thermodynamics II professor will be requiring some answers in btu, which makes it about as important as the slug for me considering how it would see regular use and can’t be derived from existing units and constants on the calculator.

[farinc]

I would say that as a chemical engineering student in the US, we use most of the units above fairly frequently (except for poundal and slug, but don't matter). I believe this would be very attractive for many students in my field and related. I also agree that the given support is not ideal when working in the odd units we work with. The numworks calculator already does all of what I need (and more) with this being the only downside (especially given that physics/chemistry constants are not just numbers but have units also). Please consider this a priority!

[adri1numworks]

Hello, Thank you for your suggestions !

For now, we consider keeping only the most common units. Among the units above, we will implement the cal and kcal in a future version. Concerning pounds per square inch : this is feasible by dividing any mass by a surface, just as in the metric system.

Then, the other units are not planned to be implemented any time soon. As such I close this ticket. We might reopen it if we reconsider this.

[mobluse]

The pound in the pressure unit pounds per square inch (psi) is not 1-pound mass, but 1-pound force. To convert psi to pascal one needs to multiply 1-pound mass in kilogram by g (9.81 m/s^2) and divide by a square inch in meters: (_lb_g0)/_in^2. But it doesn't work now in Numworks with e.g. 6.89E3_Pa→(_lb_g0)/_in^2 or 6.89E3_Pa→_lb_g0/_in^2. It works in Texas Instruments TI-89 with 6.89E3_Pa→_psi which is .99931_psi (In TI-89 unit conversion → is filled >).

[eclecticfluff]

Also worth noting is that since US education puts equal emphasis on SI and US customary measurments. As it stands, the SI units included cover more than enough range to function in college level engineering and science courses while the US customary units included can only cover late elementery school subjects with workarounds. Unless the intent of including feet, pounds, Farenheit, etc. is on the off chance that a student in a fully metricized country might come across them I don′t see the point of this half measure. Admittedly inH2O, inHg, kip, ksi, pdl, and slug are less common even within the US system, but that still leaves a lot of vital units out. Even if gravities become usable as a unit, that does′t change how any problem as or more advanced than basic physics requires restating US derrived unit definitions and forcing of unit conversions. Common US units for energy, absolute temperature, force, and pressure exist. Btu for energy, °R for absolute temperature, lbf for force, and psi for pressure. Also, what is the present way of determining whether a unit is common? In my experience, hp is about as common as btu while the long ton is way less common than the short ton.

[eclecticfluff]

I have tried to gather a comparison of units available on the current flagship models by other calculator manufacturers in hopes that it may be more persuasive. Note that I skipped over fully written out derived and undocumented units. Nevertheless, this should provide a good picture of what the glaring are for the calculator.  category	name	casio fx-CG50	hp prime	TI Nspire	Numworks
Length	fermi	fm	fermi	fm
	angstrom	Å	Å	Å
	meter	m	m	m	m
	astronomical unit	AU	au	au	au
	light year	l.y.	lyr	ltyr	ly
	parsec	pc	pc	pc	pc
	thousandth of an inch	Mil	Mil	mil
	inch	in	in	in	in
	US survey foot		ftUS
	foot	ft	ft	ft	ft
	yard	yd	yd	yd	yd
	fathom	fath	fath	fath
	rod	rd	rd	rd
	chain		chain
	US survey mile		miUS
	statue mile	mile	mi	mi	mi
	nautical mile	n mile	nmi	Nmi
Area	hectare	ha	ha	ha	ha
	are		a
	acre	acre	acre	acre	acre
	barn		b
Volume	stere		st
	liter	L	l	l	L
	US fluid oz	fl_oz(US)	ozfl	floz	floz
	UK fluid oz	fl_oz(UK)	ozUK	flozUK
	US gallon	gal(US)	gal	gal	gal
	UK gallon	gal(UK)	galUK	galUK
	Canadian gallon		galC
	pint	pt	liqpt	pt	pt
	US quart		ptUK
	quart	qt	qt	qt	qt
	teaspoon	tsp	tsp	tsp	tsp
	tablespoon	tbsp	tbsp	tbsp	tbsp
	cup	cup	cu	cup	cup
	barrel		bbl
	bushel		buUS
	peck		pk
	board foot		fbm
time	second	s	s	s	s
	minute	min	min	min	min
	hour	h	h	hr	h
	day	day	day	day	day
	week	week		week	week
	month				month
	year	yr	yr	yr	year
	sidereal year	s-yr
	tropical year	t-yr
	hertz		Hz
Temperature	degrees Celsius	°C	°C	°C	°C
	kelvin	K	K	K	K
	degrees Fahrenheit	°F	°F	°F	°F
	degrees Rankine	°R	Rankine	°R
Velocity	kilometer per hour		kph
	knot	knot	knot	knot
	mile per hour		mph
Acceleration	std gravity	grav
	gal	Gal
Mass	atomic mass unit	u	u	amu
	carat		ct
	kilogram	kg	kg	kg	kg
	metric ton	mton	t	mton	t
	avoirdupois ounce mass	oz	oz	oz	oz
	avoirdupois pound mass	lb	lb	lb	lb
	slug	slug	slug	slug
	short ton	ton(short)	tonUS	tonUS	shtn
	long ton	ton(long)	tonUK	tonUK	lgtn
	grain		grain
	tropy ounce mass		ozt
	troy pound mass		lbt
Force	newton	N	N	N	N
	dyne	dyne	dyn	dyne
	gram force		gf
	kologram force	kgf		kgf
	ounce force		ozf
	pound force	lbf	lbf	lbf
	kilopound force		kip
	ton force	tonf		tonf
Pressure	pascal	Pa	Pa	Pa	Pa
	millimeter of water	mmH₂O		mmH₂O
	millimeter of Mercury	mmHg	mmHg	mmHg
	atmosphere	atm	atm	atm	atm
	inch of water	inH₂O	inH2O	inH₂O
	inch of Mercury	inHg	inHg	inHg
	pound per square inch		psi	psi
	bar	bar	bar	bar	bar
	torr		torr	torr
Energy & work	electron Volt	eV	eV	eV	eV
	joule	J	J	J	J
	watt hour		Wh
	kilowatt hour			kWh
	foot pound			ftlb
	thermochemical calorie	calₜₕ
	calorie (15°C)	cal₁₅
	international calorie	calIT	cal	cal
	thermochemical kilocalorie	kcalₜₕ
	kilocalorie (15°C)	kcal₁₅
	international kilocalorie	kcalT	kcal	kcal
	liter atmosphere	l-atm		latm
	British thermal unit IT	Btu	Btu	BTU
	erg	erg	erg	erg
	EEC therm		thermEC
	US therm		thermUS
	UK therm		thermUK
	tonne of oil equivalent		toe
	tonne of ?		tec
	liter of ?		lep
	barrel of ?		bblep
	barrel of oil equivalent		boe
	cubic foot gas		cf
Power	watt	W	W	W	W
	metric horsepower			PS
	horsepower	hp	hp	hp
electromagnetic	amp		A		A
	volt		V		V
	culomb		C		C
	ohm		Ohm		Ω
	farad		F		F
	faraday		Fdy
	weber		Wb
	henry		H		H
	inverse ohm		mho
	Siemens		S		S
	tesla		T		T
light	candela		cd		cd
	foot-lambert		flam
Viscocity	Poise		P
	stokes		St
Radiation	becquerel		Bq
	curie		Ci
	gray		Gy
	rad		rd
	roentgen equivalent man		rem
	sievert		Sv
	roentgen		R