# Common Unit Conversions

For many transformations, particularly when automated, please use the udunits2 software where possible. For example, in R, you can use

```
library(udunits2)
## transform meters to mm
ud.convert(10, "m", "mm")
## equivalently, via the udunits synonym database
ud.convert(10, "meters", "millimeters")
## it can also handle more complex units
ud.convert(10, "m/s", "mm/d")
```

NB: Many of these conversions have been automated within [PEcAn](https://github.com/PecanProject/pecan).

**Useful conversions for entering site, management, yield, and trait data \label{tab:conversions}**

| From ((X))                   | to ((Y))                                 | Conversion                                                       | Notes                                                                               |
| ---------------------------- | ---------------------------------------- | ---------------------------------------------------------------- | ----------------------------------------------------------------------------------- |
| (X\_2=)root production       | (X\_1=)root biomass & root turnover rate | (Y = X\_2/X\_1)                                                  | Gill \[2000]                                                                        |
| DD(^{\circ}) MM'SS           | XX.ZZZZ                                  | (\textrm{XX.ZZZZ} = \textrm{XX} + \textrm{MM}/60+\textrm{SS}/60) | to convert latitude or longitude from degrees, minutes, seconds to  decimal degrees |
| lb                           | kg                                       | (Y=X\times 2.2)                                                  |                                                                                     |
| mm/s                         | (\mu) mol CO(\_2) m(^{2}) s(^{-1})       | (Y=X\times 0.04)                                                 |                                                                                     |
| m(^2)                        | ha                                       | (Y = X/10^6)                                                     |                                                                                     |
| g/m(^2)                      | kg/ha                                    | (Y=X\times 10)                                                   |                                                                                     |
| US ton/acre                  | Mg/ha                                    | (Y = X\times 2.24)                                               |                                                                                     |
| m(^3)/ha                     | cm                                       | (Y=X/100)                                                        | units used for irrigation and rainfall                                              |
| % roots                      | root:shoot (q)                           | (Y=\frac{X}{1-X})                                                | (\\% \text{roots} = \frac{\text{root biomass}}{\text{total biomass}})               |
| (\mu) mol cm(^{-2}) s(^{-1}) | mmol m(^{-2}) s(^{-1})                   | (Y = X/10)                                                       |                                                                                     |
| mol m(^{-2}) s(^{-1})        | mmol m(^{-2}) s(^{-1})                   | (Y = X/10^6)                                                     |                                                                                     |
| mol  m(^{-2}) s(^{-1})       | (\mu) mol cm(^{-2}) s(^{-1})             | (Y = X/ 10^5)                                                    |                                                                                     |
| mm s(^{-2})                  | mmol m(^{-3}) s(^{-1})                   | (Y=X/41)                                                         | Korner et al. \[1988]                                                               |
| mg CO(\_2) g(^{-1}) h(^{-1}) | (\mu) mol kg(^{-1}) s(^{-1})             | (Y = X\times 6.31)                                               | used for root\_respiration\_rate                                                    |
| (\mu) mol                    | mol                                      | (Y= X\times 10^6)                                                |                                                                                     |
| julian day (1--365)          | date                                     |                                                                  | see ref: <http://disc.gsfc.nasa.gov/julian_calendar.shtml> (NASA Julian Calendar)   |
| spacing (m)                  | density (plants m(^{2}))                 | (Y=\frac{1}{\textrm{row spacing}\times\textrm{plant spacing}})   |                                                                                     |
| kg ha(^{-1}) y(^{-1})        | Mg ha(^{-1}) y(^{-1})                    | (Y= X/1000)                                                      |                                                                                     |
| g m(^{-2}) y(^{-1})          | Mg ha(^{-1}) y(^{-1})                    | (Y= X/100)                                                       |                                                                                     |
| kg                           | mg                                       | (Y=X\times 10^6)                                                 |                                                                                     |
| cm(^2)                       | m(^2)                                    | (Y=X\times 10^4)                                                 |                                                                                     |