The qty function makes it easy to keep track of different quantities in chemical calculations. Metric prefixes are fully supported, i.e. any unit can be combined with standard metric_scaling scaling (mL, nmol, kg, etc.). Some quantities can also be used in common arithmetic operations.

qty(x = double(), unit, scale_to_best_metric = TRUE)



the numeric value of the quantity, can be a single value or a vector


the unit of the quantity


whether to automatically scale to the best metric prefix


The following types of quantities are supported.

amount (N): base unit mol but also understands mole, all metric prefixes allowed

mass (m): base unit g, all metric prefixes allowed

molecular weight (MW): base unit g/mol, all metric prefixes allowed in the numerator

molarity concentration (C): base unit M but also understands mol/L, all metric prefixes allowed in the numerator

mass concentration (C): base unit g/L but also understands g/l, all metric prefixes allowed in the numerator. This is technically a density and sometimes referred to as such in the microbial kitchen documentation.

volume (V): base unit L but also understands l, all metric prefixes allowed

pressure (P): base unit bar but also understands Pa, all metric prefixes allowed, the common non-metric units atm, psi, Torr, mTorr, and % SP (% at standard pressure = % of 1 bar) are also supported and will be automatically converted to bar.

gas solubility (S): base unit M/bar, all metric prefixes allowed in the numerator, the common non-metric unit M/atm is also supported and will be automatically converted to M/bar. This quantity is used for capturing Henry's law constants.

temperature (T): base unit K but also understands C and F and converts them to Kelvin


  • qty: generate a quantity object

See also


qty(0.045, "mmol/L")
#> <C (molarity concentration) in 'µM'[1]> #> [1] 45
qty(200, "mbar")
#> <P (pressure) in 'mbar'[1]> #> [1] 200
qty(6, "psi")
#> <P (pressure) in 'mbar'[1]> #> [1] 413.6855
qty(30, "C")
#> <T (temperature) in 'K'[1]> #> [1] 303.15
qty(100, "K")
#> <T (temperature) in 'K'[1]> #> [1] 100
qty(5, "mg/L")
#> <C (mass concentration) in 'mg/L'[1]> #> [1] 5
qty(1, "mM/bar")
#> <S (gas solubility) in 'mM/bar'[1]> #> [1] 1
qty(257, "g/mol")
#> <MW (molecular weight) in 'g/mol'[1]> #> [1] 257