| Abbreviation | Definition |
|---|---|
| grs. | grains |
| GRT | Gross Registered Tons |
| GSF | Gross Square Feet |
| GSM | Grams per Square Meter |
| GT | Gross Tonnage |
| gt. | drop |
| GtC | Gigatons of Carbon |
| gtt. | drops |
| GW | Gigawatt |
| GWAM | Gross Words A Minute |
| GWH | GigaWatt Hour |
| GWTH | gigawatts-thermal |
| Gy | Gray (= 100 Rads; units of irradiation) |
| H | Half |
| H | Height |
| H | Hour |
| HA | Hectare |
| HA | Hour Angle |
| HASL | Height Above Sea Level |
| HBU | Homebrew Bitterness Unit |