Metric Tons to Kilograms

Company Reports Count Tonnes, Everyday Choices Count Kilograms

An annual sustainability report says the business cut 480 t CO₂e last year. A flight calculator, opened on the same afternoon, says the trip you are about to book is worth 230 kg CO₂e. Both numbers describe the same substance, measured the same way, yet they sit three orders of magnitude apart and neither page bothers to bridge the gap.

That gap is where footprint arithmetic quietly falls apart. Emission factors for meals, journeys, appliances and single products are published in kilograms because that is the size of the thing being measured; targets, inventories and national statistics are published in tonnes because anything smaller would run to seven digits. Line the two up and a personal choice can be weighed honestly against an organisational claim.

Conversion factor: 1 t = 1000 kg exactly, so kg = t × 1000. That 480 t reduction is 480 000 kg CO₂e, and the 230 kg flight is 0.23 t — roughly two thousandths of it.

Which Scale a Carbon Figure Arrives On

Inventories and targets use tonnes

A corporate inventory, a science-based target and a country's annual total are all stated in tonnes, and often in kilotonnes or megatonnes once the numbers get large enough.

Journeys and meals arrive in kilograms

Anything you can personally verify — a flight leg, a hundred kilometres of driving, a dinner, a month of home electricity — comes out of the calculator in kilograms.

Product footprints drop to grams

Packaged food carbon labels are printed per 100 g of product, so their footprints often land in grams. Three unit steps can separate a label from the report that quotes it.

Per-capita shares stay in tonnes

Average annual emissions per person are published as a handful of tonnes, which is the only reference point that makes an individual activity figure mean anything.

Putting a Footprint Figure on One Scale

The point is to end up with a single column of comparable numbers rather than a mix of report figures and calculator outputs.

Type the tonnage from the report

Enter the tonne figure in the left field and the kilogram equivalent appears as you type — there is no convert button. A comma or a dot both read as the decimal mark, and any spaces you paste in are ignored, so 1,75 and 12 400 parse fine.

Go the other way for a calculator output

Both boxes accept typing, so a 230 kg result can be keyed straight into the right-hand field to read 0.23 t. The swap button (↔) reverses the pair outright when everything you are handling comes in kilograms.

Drop to grams for a pack label

Search either dropdown for gram when a carbon label quotes a per-100 g figure. Values below one millionth switch to scientific notation, so a very small share of a tonne still shows something readable.

Copy the bare figure into the sheet

Each field has a copy button that hands over the digits alone, with no unit and no thousands spacing, which is what a footprint spreadsheet wants in the cell. Selecting inside a field and pressing Ctrl + C strips the spacing too.

Convert the unit, not the method: two footprint numbers only become comparable once they share a boundary as well as a unit. A figure that covers manufacturing plus shipping cannot be added to one that covers use-phase energy alone, however tidily they now both read in kilograms.

Everyday Activities Weighed Against a Tonne

These are indicative ranges rather than fixed constants. Every one of them moves with the country, the electricity mix, the supply chain and the accounting method behind the estimate, so treat them as a sense of scale — enough to see which decisions are worth arguing about.

Activity	Typical kg CO₂e	Same in tonnes	What moves the figure
Long-haul flight, one way, economy	400 – 900 kg	0.4 – 0.9 t	Distance, load factor, and whether non-CO₂ effects are counted
Short-haul flight, one way, economy	100 – 200 kg	0.1 – 0.2 t	Take-off and climb dominate, so short legs are worse per kilometre
100 km in a petrol car	15 – 25 kg	0.015 – 0.025 t	Falls per person as passengers are added
100 kWh of grid electricity	2 – 45 kg	0.002 – 0.045 t	Almost entirely the grid mix; hydro and nuclear sit near the bottom
One beef-based main course	4 – 9 kg	0.004 – 0.009 t	Ruminant methane and land use, not the cooking
One lentil or bean main course	0.3 – 1 kg	0.0003 – 0.001 t	Roughly an order of magnitude below the beef plate
Manufacturing one smartphone	40 – 90 kg	0.04 – 0.09 t	Mostly chip fabrication; charging it for a year adds only a few kg
One cotton T-shirt	2 – 8 kg	0.002 – 0.008 t	Fibre, dyeing and finishing energy; washing adds more over its life

Read down the tonne column and the shape of the problem shows itself. Nothing on a single-item basis reaches a tonne except flying, and the household entries differ by a factor of a hundred between top and bottom. A per-person annual footprint of a few tonnes is therefore not built out of T-shirts; it is built out of heating, driving, flying and food, repeated all year.

What Helps While You Are Adding Emissions Up

Instant rescaling of a report line

The second field tracks every keystroke, so a whole column of tonne figures can be worked through without stopping to press anything.

Grams within reach for labels

The searchable dropdowns cover all 18 weight units, so a per-100 g pack figure and a corporate tonnage can be brought onto the same row.

Both directions without reloading

Type into either box, or press swap, depending on whether you are scaling a target down to an activity or an activity up to a target.

Clean values for a footprint sheet

Copy returns the number with nothing attached, so the cell stays numeric and your totals keep adding up.

Questions About Carbon Units and Reporting

What does the "e" in CO₂e actually stand for?

Equivalent. Greenhouse gases are not equally potent, so each one is multiplied by a global warming potential — normally the 100-year value, GWP100 — and expressed as the amount of carbon dioxide that would warm the planet by the same amount. Under the IPCC's sixth assessment, fossil methane carries a GWP100 of roughly 30 and nitrous oxide close to 270, while some refrigerant gases run into the thousands. That is why a single kilogram of methane leaking from a pipe appears in an inventory as tens of kilograms of CO₂e, and why livestock and refrigeration loom much larger in a footprint than their raw gas mass suggests.

Is a tonne of CO₂e the same thing as a metric ton or a megagram?

Yes, all three are 1000 kg. "Tonne" is the spelling used almost everywhere outside the United States and throughout IPCC material; "metric ton" is written out in full in US reporting precisely because an unqualified American ton means something else; and "megagram" (Mg) is the strictly SI form, correct but almost never seen in a climate document. In climate work the tonne is effectively universal, which is why an inventory expressed in tonnes is safe to read without first checking which country published it.

What are Scope 1, 2 and 3 in one plain sentence each?

Scope 1 is what the organisation burns itself: boilers, furnaces, its own vehicles. Scope 2 is the energy it buys, mostly electricity, whose emissions happen at the power station. Scope 3 is everything else along the value chain, from purchased goods and business travel through to how customers use and dispose of the product. Scope 3 is usually the largest by a wide margin and the least certain, so a headline tonnage should always be read alongside a statement of which scopes it covers.

Why are national and per-person figures in tonnes when a pack label uses grams?

Each unit is chosen so the interesting digits sit at the front. A person's annual emissions run to several tonnes, a country's to hundreds of megatonnes, and writing either in kilograms would bury the meaning in zeros. A ready meal sits at a few hundred grams of CO₂e per 100 g of food, which would round away to nothing in tonnes. The unit signals the intended scale of the comparison, and a label figure only becomes an annual figure once you multiply it by how often you actually buy the thing.

Why do two calculators give different answers for the same flight?

Because they make different, mostly defensible, assumptions. One may count only the carbon dioxide from burning kerosene while another applies a multiplier for contrails and other high-altitude effects, which can roughly double the result. After that come cabin class, since a business seat is allocated several times the floor area of an economy one; assumed occupancy; whether extracting and refining the fuel is included; and whether the route is measured great-circle or with an allowance for real flight paths and holding. Read the methodology note before comparing two numbers, and never mix estimates from different tools inside a single total.