Convert Tonnes to Kilotonnes CO₂(e)
The tonne is the everyday unit of carbon accounting — a person, a vehicle, a building. The kilotonne (kt) is the next step up, where a large facility or a whole organisation lives. The conversion is pure arithmetic: 1 kilotonne = 1,000 tonnes, so to go from tonnes to kilotonnes you divide by 1,000. It works the same for CO₂ and CO₂e, because scaling a mass doesn’t depend on which gas it is.
To convert tonnes to kilotonnes of CO₂(e), divide by 1,000 (1 kt = 1,000 t). So 25,000 t CO₂e = 25 kt CO₂e. To go the other way, multiply kilotonnes by 1,000.
kt = t ÷ 1,000. Reverse: t = kt × 1,000. Both are exact SI multiples of the tonne, so there is no rounding — 1 kt is precisely 1,000 tonnes. The same factor applies whether the mass is CO₂ or CO₂e.
| Tonnes | ÷ 1,000 | Kilotonnes |
|---|---|---|
| 1,000 t | ÷ 1,000 | 1 kt |
| 25,000 t | ÷ 1,000 | 25 kt |
| 500 t | ÷ 1,000 | 0.5 kt |
| 1 t | ÷ 1,000 | 0.001 kt |
What tonnes and kilotonnes mean
Both are multiples of the metric tonne (1,000 kg), each a thousand times the last. A kilotonne is a thousand tonnes; a megatonne a million; a gigatonne a billion. The ladder makes the relationships clear — every step is ×1,000:
| Unit | Tonnes | Relation |
|---|---|---|
| Tonne (t) | 1 | 1,000 kg |
| Kilotonne (kt) | 1,000 | 1 kt = 1,000 t |
| Megatonne (Mt) | 1,000,000 | 1 Mt = 1,000 kt |
| Gigatonne (Gt) | 1,000,000,000 | 1 Gt = 1,000 Mt |
A kilotonne — 1,000 tonnes of CO₂e — is roughly the annual emissions of 230 average petrol cars (at 4.29 t each) or 130 US homes’ energy (at 7.45 t each). It is the scale of a single large building or a mid-size company, which is exactly why organisational and facility totals are often quoted in kilotonnes rather than tonnes.
Emissions at kilotonne scale
Kilotonnes bridge the gap between a single tonne and a national megatonne total. Seeing real figures across the ladder makes the conversion concrete — note how a car or home is a fraction of a kilotonne, while a country is hundreds of thousands of them:
| Annual CO₂(e) | Tonnes | Kilotonnes |
|---|---|---|
| One average petrol car | ≈ 4.29 | ≈ 0.0043 |
| One US home (all energy) | ≈ 7.45 | ≈ 0.0075 |
| ~230 cars / ~130 homes | ≈ 1,000 | 1 |
| A large coal power station | ≈ several million | ≈ thousands |
| United Kingdom | ≈ 320,000,000 | ≈ 320,000 (320 Mt) |
| World (fossil + land use) | ≈ 41,000,000,000 | ≈ 41,000,000 (41 Gt) |
Per-car and per-home figures are the US EPA equivalencies; national and world totals are from the Global Carbon Budget 2023.
A company reports a footprint of 25,000 tonnes CO₂e. To express it at facility scale, divide by 1,000: 25 kt CO₂e. That is roughly the yearly emissions of 5,800 cars — a tidy way to state a mid-size corporate total without a string of zeros.
Tonnes to kilotonnes conversion table
The table reads both ways — tonnes to kilotonnes on the left (÷ 1,000), kilotonnes back to tonnes on the right (× 1,000).
| t CO₂e | → kt (÷ 1,000) | kt CO₂e | → t (× 1,000) |
|---|---|---|---|
| 1 | 0.001 | 1 | 1,000 |
| 100 | 0.1 | 5 | 5,000 |
| 1,000 | 1 | 25 | 25,000 |
| 10,000 | 10 | 100 | 100,000 |
| 500,000 | 500 | 1,000 | 1,000,000 |
Where these units are used
- Corporate and facility reporting. A single site or a mid-size company often totals a few to a few hundred kilotonnes a year, so kilotonnes keep the numbers readable without a string of zeros.
- Emissions trading. Installations in schemes like the EU ETS report in tonnes, but large emitters — power stations, steel, cement — run into the hundreds or thousands of kilotonnes.
- Cities and sectors. A town, a transport network or an industrial cluster typically lands in the kilotonne-to-megatonne band, one rung below the national megatonne figure.
- Molecule-agnostic. Because this is a mass conversion, it serves CO₂, CO₂e and any single gas identically — CO₂e simply bundles all gases into a CO₂-equivalent mass using their global warming potentials first.
Two traps. First, a tonne and a kilotonne differ by 1,000× — it’s easy to slip a factor of a thousand, so 500 t is 0.5 kt, not 500 kt. Second, kilotonnes of CO₂ are not kilotonnes of carbon: one tonne of carbon becomes about 3.664 tonnes of CO₂, so if your source is in carbon (tC or ktC), convert to CO₂ first with the carbon-to-CO₂ converter before scaling here.
Frequently Asked Questions
Divide the tonnes by 1,000. For example, 25,000 t CO₂e ÷ 1,000 = 25 kt CO₂e. To reverse it, multiply kilotonnes by 1,000. The factor is exact and applies to CO₂ and CO₂e alike.
Exactly 1,000. A kilotonne is an SI multiple of the tonne — the “kilo” prefix means a thousand — so one kilotonne is a thousand tonnes, or a million kilograms.
Roughly the yearly emissions of 230 average petrol cars, or 130 US homes’ energy use. It is the scale of a single large building or a mid-size company — a useful unit when tonnes would run to five or six digits.
Once a total runs into the tens of thousands of tonnes, kilotonnes keep it readable. Corporate, facility, city and sector footprints are often reported in kilotonnes; individual, vehicle and building figures stay in tonnes.
Every step up the ladder is ×1,000: 1,000 kt = 1 Mt, and 1,000 Mt = 1 Gt. So a national total of 320 megatonnes is 320,000 kilotonnes, and the ~41-gigatonne world total is 41 million kilotonnes.
No. Scaling a mass by 1,000 doesn’t depend on which gas it is, so the tonne-to-kilotonne factor is identical for CO₂, CO₂e or any single greenhouse gas. CO₂e just means the gases have already been combined into a CO₂-equivalent mass using their global warming potentials.
No — and mixing them up is a common error. One tonne of carbon becomes about 3.664 tonnes of CO₂, so kt of carbon and kt of CO₂ differ by that factor. This converter only scales t↔kt of the same quantity. If your source is in carbon (tC or ktC), convert to CO₂ first with the carbon-to-CO₂ converter.