Bovnar — Units & Currencies Cheat Sheet

Bovnar (BVNR) v1.1 documentation · Also available as Markdown and PDF.

Spec version: 1.1 Status: Reference — the symbol tables of the unit and currency registry Scope: 264 physical units, 166 fiat currencies, 50 cryptocurrencies, and every SI/IEC prefix.

Table of Contents

1. SI Prefixes
2. IEC Binary Prefixes
3. Prefix Validity Rules
4. Physical Units
   • 4.1 SI Base Units
   • 4.2 Named SI-Derived Units
   • 4.3 Non-SI Units Accepted with SI
   • 4.4 Imperial & US Customary — Length
   • 4.5 Imperial & US Customary — Mass
   • 4.6 Temperature
   • 4.7 Pressure
   • 4.8 Energy
   • 4.9 Power
   • 4.10 Force
   • 4.11 Speed & Rotation
   • 4.12 Acceleration
   • 4.13 Volume — US Liquid
   • 4.14 Volume — UK Imperial
   • 4.15 Volume — US Apothecary & Dry
   • 4.16 Area
   • 4.17 Angle
   • 4.18 Digital
   • 4.19 CGS Units
   • 4.20 Radiation
   • 4.21 Logarithmic
   • 4.22 Electrical Power
   • 4.23 Textile Linear Density
   • 4.24 Old German Units
   • 4.25 Additional Physical Units
   • 4.26 Ratio and Proportion
   • 4.27 Named Speeds & Acidity
   • 4.28 Water Hardness
   • 4.29 Water-Quality Instrument Scales
   • 4.30 Survey, Typographic, Dry-Volume and Trade Units
5. Currencies
   • 5.1 The Mandatory Currency Sigil
   • 5.2 ISO 4217 Fiat Currencies
   • 5.3 Cryptocurrencies
   • 5.4 Currency Prefix Rules
6. Symbol Disambiguation

• See also

1. SI Prefixes

Written as prefix~base, or compactly without the separator: k~m and km are both the kilometre. The canonical output form always keeps the ~.

µ is U+00B5 MICRO SIGN (UTF-8 0xC2 0xB5). U+03BC (Greek small letter mu) is also accepted on input; the canonical output is always U+00B5. ASCII u is accepted as an input-only alias for µ (e.g. u~m = µ~m); the canonical output is always µ. da is a two-character prefix: da~m = decametre.

Prefix–base ambiguities — the base unit is the longest alias suffix, so a bare token is always the unit; ~ selects the prefix reading:

Examples: bare m = metre; m~s and ms = millisecond. Bare d = day; d~s and ds = decisecond. Bare min = minute, so milli-inch needs the separator: m~in.

A compact spelling is refused when the token means something else in the wild: usb and kt are error_unit_illegal (write u~sb; for kt, k~t for the kilotonne or kn for the knot). pH, mph and kph are units in their own right (§3.26–3.27 of the unit-system reference), so they parse as acidity and the two speeds — p~H, m~ph and k~ph are still the picohenry and the milli-/kilophot.

Currencies take the compact prefix too (k$EUR = k~$EUR, §5.4), but their $ sigil is never optional.

2. IEC Binary Prefixes

Used only on b (bit) and B (byte). Written as prefix~base or compactly: Ki~B and KiB are both the kibibyte.

† Ri/Qi are a forward-looking extension: IEC 80000-13 stops at yobi (Yi, 2⁸⁰).

3. Prefix Validity Rules

4. Physical Units

Symbol = canonical serialized form (produced on output; accepted on input). Long forms = accepted on input only; never produced on output. Factor = conversion factor to SI base units unless noted.

4.1 SI Base Units

g (gram) is the base symbol; k~g = kilogram.

4.2 Named SI-Derived Units

4.3 Non-SI Units Accepted with SI

4.4 Imperial & US Customary — Length

thou and mil are synonyms. Canonical output is thou. mil does not mean milliradian; milliradians are written m~rad.

4.5 Imperial & US Customary — Mass

dr_ap is 2.2× the avoirdupois dr, and the short hundredweight is exactly h~lb, so it has no unit of its own.

4.6 Temperature

Kelvin (K) is in §4.1. R is reserved for röntgen (§4.20). N alone is newton (§4.2); use °N or degN for Newton temperature.

Temperature differences. Every scale above is a scale: 25 °C is 298.15 K. A difference of 25 degrees is 25 K, and these are the units for it. Each is a ratio scale (no offset) carrying the temperature-interval quantity kind, so ΔK never converts to K and °C never converts to Δ°C — those are error_unit_mismatch.

Δ is U+0394; every unit here has ASCII spellings. There is deliberately no bare delta_C or delta_F — those read as a delta coulomb and a delta farad. Inside a compound the distinction does not arise and is not made: W/(m²·ΔK) and W/(m²·K) are the same unit, because an affine scale cannot appear in a compound at all, so the K there was already an interval.

4.7 Pressure

at ≠ atm: 1 at = 98 066.5 Pa; 1 atm = 101 325 Pa.

4.8 Energy

BTU (all-caps) is a valid alias: with no $ sigil the token is a physical-unit lookup (the currency table is only consulted for $-prefixed tokens), and it matches bu_btu. Btu and btu are also accepted.

4.9 Power

4.10 Force

4.11 Speed & Rotation

4.12 Acceleration

4.13 Volume — US Liquid

cup (lowercase) = US cup; CUP (uppercase) = Cuban Peso. See §6.

4.14 Volume — UK Imperial

4.15 Volume — US Apothecary & Dry

minim not min (which is the minute).

4.16 Area

4.17 Angle

4.18 Digital

b and B are separate quantity kinds: b → B is refused, not divided by eight. Prefixes still convert within each (Ki~B → B is 1024). See doc/05 §3.17.

4.19 CGS Units

4.20 Radiation

4.21 Logarithmic

Relating two logarithmic scales is a change of base, not a multiplication, so the conversion engine cannot express it — and dB is written against both the power (10·log₁₀) and field (20·log₁₀) conventions without the annotation saying which. The library refuses the pair. See doc/05 §3.15.

4.22 Electrical Power

W, var, and VA all have SI dimension kg·m²·s⁻³. bvn_units_compatible returns true across them; use .components[0].base to distinguish.

4.23 Textile Linear Density

9 den = 1 tex.

4.24 Old German Units

No Old German unit accepts any SI or IEC prefix (bvn_prefix_unit_valid rejects all non-si_none prefixes for bu_pfund … bu_scheffel). Enum values 100133–100145.

Mass (metric-compatible)

Length (historical Prussian)

Area (historical Prussian)

Volume (historical Prussian)

4.25 Additional Physical Units

Length

Mass

Signal Rate

SI prefixes are accepted on all units in this section. IEC prefixes are rejected for all non-digital units.

4.26 Ratio and Proportion

Dimensionless scaling factors: 5 % ≡ 0.05, 250 ppm ≡ 0.00025. These do not accept SI or IEC prefixes.

4.27 Named Speeds & Acidity

mi/h and k~m/h are the same quantities written as compounds; both spellings are valid, but a named unit and its compound do not reconcile inside one value. pH is not p~H (picohenry), and ph is the phot.

4.28 Water Hardness

Six scales for one quantity — the concentration of dissolved alkaline-earth ions. All carry mol·m⁻³ and convert into each other and into m~mol/L. None takes a prefix.

Keep the degree sign: dH without it is the decihenry. Water chemistry's "ppm" is °aH, not Bovnar's dimensionless ppm. Millimoles per litre is just the compound m~mol/L, and meq/L is the same unit as mval/L. gpg (amount concentration) is not gr/gal (mass concentration).

Conductivity and dissolved solids need no units of their own: EC is µS/cm, mS/cm, dS/m or S/m (µmho/cm too — mho/℧ are the siemens); TDS is mg/L; resistivity is MΩ·cm. "TDS in ppm" means mg/L, while Bovnar's ppm is the dimensionless 10⁻⁶.

4.29 Water-Quality Instrument Scales

The five turbidity scales agree on a formazin standard and not on real water — and FAU is not even the same optical quantity (attenuation, not scatter), while JTU is visual and relates to formazin only near 40 units. Bovnar refuses every conversion between them; report the method. JTU and PSU take no prefix. PSU is a conductivity ratio, not a mass fraction — for absolute salinity write g/k~g. Case matters: cF is the centifarad and fau the femto-astronomical-unit.

4.30 Survey, Typographic, Dry-Volume and Trade Units

Every unit here was, until it was added, the sole reason a run of UCUM, UDUNITS-2, QUDT, OM or UN/ECE codes had to be refused. All are exact; the ones whose value is not a terminating decimal in SI state a rational rather than a rounded double.

US survey lengths

ftUS (§4.4) has always been here and nothing was built on it. These are exact rational multiples of it, and the survey foot is 2 ppm longer than the international one — which is small enough to ignore and never small enough to be right.

The survey foot was withdrawn for new work at the end of 2022. That is a reason to read it carefully, not to refuse it: US land records, state-plane coordinates and a century of drawings are written in these. ac vs acUS differ by 4 ppm — twice the foot's 2 ppm, an area being a length squared — which is about ten square metres on a section of land.

Typographic lengths

The symbols are not pt and ln: pt is the pint. A length answering to pt would be the same collision as kt for the knot, which §6 refuses outright. The printer's point (0.013837 in) is a different unit and is carried separately, as pnt_pr below.

US dry volumes and the trade measures

A dry quart is 16 % larger than the liquid qt. The peck and bushel here have always been the dry ones; the gallon, quart and pint were only the liquid ones.

ac_ft is built on the survey acre and foot, which is what UDUNITS, OM and every US water agency mean by an acre-foot. The international one is ac·ft = 1233.48183754752 m³.

And the singles

darcy takes prefixes, so the millidarcy every reservoir report is written in is m~darcy. thm_ec is the European gas-billing therm; native thm is the US therm, 0.24 % away.

Nine more the unit profiles needed

Each was refused across UCUM, UDUNITS-2, QUDT and OM for want of a native unit of the magnitude, and every factor below is one two or three publishers state independently, agreeing to the last digit.

Each is a near neighbour of a unit already here, which is why it needed a row rather than an alias: pnt_pr is 0.37 % off pnt, hp_E 0.04 % off hp, bsh_uk 3.2 % off bsh, and hp_B thirteen times any horsepower. abV needed a unit because no decade prefix reaches 10⁻⁸ and prefixes do not stack. AT and debye are exact rationals — 175/6 g, and 10⁻²¹/c C·m, exact since the 2019 SI fixed c — of which their publishers state 7- and 6-digit roundings.

And the thirty-five the same sweep found next

The rest of the refusals two or more vocabularies define. Where publishers disagree the exact definition decides: the CGS-ESU units are built on c, exact since 2019, so their five- to seven-digit decimals are roundings of the rational stated here. The π-based rows carry .exact = false. yr is still the Julian year — naming the other calendars is what lets a UDUNITS or CF document that says year be read at all.

Calendar and sidereal time

CGS electrostatic (ESU)

Luminance

Water-vapour permeance

Heat conventions

And the singles

5. Currencies

5.1 The Mandatory Currency Sigil

As of spec 1.0 a currency code carries a mandatory $ sigil: write $USD, $BTC, k~$EUR (or compactly k$EUR), $USD/oz_t. The codes listed in the tables below are the bare ISO 4217 / crypto identifiers — prefix each with $ when you use it in a document. A bare code (no $) is not a currency; it is matched against the physical-unit table and raises error_unit_illegal if it is not a unit. This removes every currency/unit namespace collision (e.g. $CUP the Cuban Peso vs cup the unit).

5.2 ISO 4217 Fiat Currencies

166 codes at ids 900000 … 900165, the front of block 90 of the value_base_unit_t id space (BVN_CURRENCY_FIRST …). They have no named bu_* enumerators — they are resolved from the $-sigil code by bvn_parse_currency_str and carried as the numeric base value; query them with bvn_unit_is_fiat / bvn_currency_info, both of which read the catalogue row rather than testing the id's range.

Min = minor unit exponent N: 1 major unit = 10^N minor units (e.g. 1 USD = 100 cents, N=2). Minor units are bold when they differ from 2. numeric_code is the ISO 4217 numeric identifier.

CLF is the only currency with 4 minor units. XTS is the ISO 4217 testing code; present in the table but should not appear in production data.

5.3 Cryptocurrencies

50 codes at ids 900166 … 900215, after the fiat codes in the same block 90. Like them they have no named bu_* enumerators — resolved by bvn_parse_currency_str, queried with bvn_unit_is_crypto / bvn_currency_info. numeric_code = 0 for all.

Min = minor_unit = on-chain decimal places. E.g. <uint:64,$BTC> stores satoshis; divide by 10⁸ to obtain BTC.

5.4 Currency Prefix Rules

All 24 SI prefixes are allowed on all currency units. IEC binary prefixes are forbidden on all currencies (error_unit_illegal). The ~ is optional — the $ sigil already separates the prefix from the code — but the sigil is not: kUSD is error_unit_illegal.

6. Symbol Disambiguation

The full token-by-token treatment — case traps, look-alike code points, same-dimension quantities, and abbreviations that are deliberately not units — is in 07_bovnar_unit_ambiguities.md.

As of spec 1.0 a currency is written only with the $ sigil (§5.1), so the bare form is always a physical-unit lookup and the namespaces never collide:

No bare token is simultaneously a valid physical unit and a currency: currencies live entirely under $, physical units entirely without it.

See also

• Unit & Currency Reference — the full registry: dimensions, factors, prefix policy, and the C API
• Unit Ambiguities — which reading wins when a token could mean two things
• Specification §11 — Units System — how a unit attaches to a value
• FAQ §4 — Units — the questions these tables raise most often
• Unit Profiles — writing these same units as UCUM, UNECE, QUDT or UDUNITS codes, and the profile-only units that exist in no native spelling

The id space is blocked: the leading two digits of an id name its vocabulary. Native units 100000–100263 (264) · UCUM opaque units 200000–200040 (41) · UN/ECE opaque units 300000–300024 (25) · currencies 900000–900215 (166 fiat, 50 crypto). Blocks 40, 50, 60, 70 and 80 are reserved for QUDT, QUDT quantity kinds, UDUNITS, OM 2 and the CF standard names, which contribute no opaque units today. The space is SPARSE — do not index an array by an id. BVN_UNIT_SLOT_COUNT = 331 is the row count of the library's dense tables, indexed by bvni_unit_slot(), and is not a bound on the enum.

End of Bovnar — Units & Currencies Cheat Sheet (Bovnar spec 1.1).