Editing Tonne (section)

==Derived units==
As a non-SI unit, the use of SI metric prefixes with the tonne does not fall within the SI standard.  For multiples of the tonne, it is more usual to speak of thousands or millions of tonnes. Kilotonne, megatonne, and gigatonne are more usually used for the energy of nuclear explosions and other events in [[TNT equivalent|equivalent mass of TNT]], often loosely as approximate figures.  When used in this context, there is little need to distinguish between metric and other tons, and the unit is spelled either as ''ton'' or ''tonne'' with the relevant prefix attached.{{efn|The Oxford English Dictionary 2nd ed. gives both megaton and megatonne and adds "The unit may be calculated in either imperial or metric tons; the form megatonne generally implies the metric unit". The use for energy is the first definition; use for mass or weight is the third definition.}}
{|class="wikitable" style="text-align:center"
|-
! colspan=2 | Tonnes
! colspan=2 | Grams
! colspan=3 | Equivalents<ref group="table">The equivalent units columns use the [[short scale]] large-number naming system currently used in most English-language countries, e.g. 1&nbsp;billion = 1000&nbsp;million = {{val|1,000,000,000}}.</ref>
|-
! Name           !! Symbol
! Name           !! Symbol
! Tonnes (t)     !! Short Tons (tn)<ref name="rounding" group="table">Values in the equivalent short and long tons columns are [[Rounding|rounded]] to five [[significant figures]]. See [[#Conversions|Conversions]] for exact values.</ref> !! Long Tons (LT)<ref name="rounding" group="table"/>
|-
|     tonne  ||t
|  megagram  ||Mg
|1 t                || {{convert|1|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;tn || {{convert|1|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;LT
|-
| kilotonne  ||kt<ref group="table">Though non-standard, the symbol "kt" is also used (instead of the standard symbol "kn") for [[knot (unit)|knot]], a unit of speed for [[aircraft]] and [[watercraft]]. The standard meaning of the symbol kt is for kilotonne.</ref>
|  gigagram  ||Gg
| 1,000 t            || {{convert|1000|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;tn || {{convert|1000|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;LT
|-
| [[Orders of magnitude (mass)#106 to 1011 kg|megatonne]]  ||Mt
|  teragram  ||Tg
| 1,000,000 t  || {{convert|1|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;million&nbsp;tn || {{convert|1000000|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;LT
|-
| gigatonne||Gt
|  petagram||Pg
| 1,000,000,000 t  || {{convert|1|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;billion&nbsp;tn || {{convert|1000|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;million&nbsp;LT
|}

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