Convert Kilotonnes to Megatonnes CO₂(e)
The kilotonne (kt) is the unit of facilities and companies; the megatonne (Mt) is the unit of nations and large sectors. Converting between them is pure arithmetic: 1 megatonne = 1,000 kilotonnes, so to go from kilotonnes to megatonnes 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 kilotonnes to megatonnes of CO₂(e), divide by 1,000 (1 Mt = 1,000 kt). So 2,500 kt CO₂e = 2.5 Mt CO₂e. To go the other way, multiply megatonnes by 1,000.
Mt = kt ÷ 1,000. Reverse: kt = Mt × 1,000. Both are exact SI multiples of the tonne, so there is no rounding — 1 Mt is precisely 1,000 kt, or one million tonnes. The same factor applies whether the mass is CO₂ or CO₂e.
| Kilotonnes | ÷ 1,000 | Megatonnes |
|---|---|---|
| 1,000 kt | ÷ 1,000 | 1 Mt |
| 2,500 kt | ÷ 1,000 | 2.5 Mt |
| 500 kt | ÷ 1,000 | 0.5 Mt |
| 1 kt | ÷ 1,000 | 0.001 Mt |
What kilotonnes and megatonnes 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. 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 megatonne — 1,000 kilotonnes, or a million tonnes of CO₂e — is roughly the annual emissions of 230,000 average petrol cars or 134,000 US homes. It is the scale of a large power station or a small country, which is why national inventories and big industrial sectors are reported in megatonnes rather than kilotonnes.
Emissions at kilotonne and megatonne scale
Megatonnes are where facility totals become national ones. Seeing real figures across the ladder makes the conversion concrete — a large plant is a few megatonnes, while a whole country is hundreds:
| Annual CO₂(e) | Kilotonnes | Megatonnes |
|---|---|---|
| A large commercial building | ≈ 1–5 | ≈ 0.001–0.005 |
| A mid-size company / facility | ≈ 10–100 | ≈ 0.01–0.1 |
| A large coal power station | ≈ 5,000–10,000 | ≈ 5–10 |
| United Kingdom | ≈ 320,000 | ≈ 320 |
| United States | ≈ 4,900,000 | ≈ 4,900 |
| World (fossil + land use) | ≈ 41,000,000 | ≈ 41,000 (41 Gt) |
Facility bands are illustrative orders of magnitude; national and world totals are from the Global Carbon Budget 2023.
A large power station emits about 6,000 kt CO₂ a year. To place it on the national scale, divide by 1,000: 6 Mt. Against the UK’s ~320 Mt total, a single such plant is nearly 2% of the country — the kind of comparison the kt→Mt step is for.
Kilotonnes to megatonnes conversion table
The table reads both ways — kilotonnes to megatonnes on the left (÷ 1,000), megatonnes back to kilotonnes on the right (× 1,000).
| kt CO₂e | → Mt (÷ 1,000) | Mt CO₂e | → kt (× 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 |
| 320,000 | 320 | 1,000 | 1,000,000 |
Where these units are used
- National inventories. A country’s annual total is usually reported in megatonnes — a few hundred to a few thousand — so the megatonne is the working unit of national climate reporting (the UK, for example, is around 320 Mt CO₂e).
- Large sectors and installations. Power, steel, cement and aviation report in megatonnes; a single large plant runs to a few megatonnes (thousands of kilotonnes) a year.
- Bridging scales. Kilotonnes are the facility and corporate unit (see the tonnes-to-kilotonnes step); the megatonne is one rung up, and the megatonne-to-gigatonne step takes you to the global 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 kilotonne and a megatonne differ by 1,000× — it’s easy to slip a factor of a thousand, so 2,500 kt is 2.5 Mt, not 2,500 Mt. Second, megatonnes of CO₂ are not megatonnes of carbon (MtC): one tonne of carbon becomes about 3.664 tonnes of CO₂, so if your source is in carbon (ktC or MtC), convert to CO₂ first with the carbon-to-CO₂ converter before scaling here.
Frequently Asked Questions
Divide the kilotonnes by 1,000. For example, 2,500 kt CO₂e ÷ 1,000 = 2.5 Mt CO₂e. To reverse it, multiply megatonnes by 1,000. The factor is exact and applies to CO₂ and CO₂e alike.
Exactly 1,000. Both are SI multiples of the tonne: a kilotonne is a thousand tonnes and a megatonne is a million tonnes, so one megatonne is a thousand kilotonnes.
A million tonnes of CO₂e — roughly the yearly emissions of 230,000 average petrol cars or 134,000 US homes. It is the scale of a large power station or a small country, which is why national totals are reported in megatonnes.
Once a total runs into the thousands of kilotonnes, megatonnes keep it readable. National inventories and large sectors (power, steel, cement, aviation) report in megatonnes; individual facilities and companies usually stay in kilotonnes.
1,000 megatonnes make a gigatonne. So the UK’s ~320 Mt is 0.32 Gt, and the ~41-gigatonne world total is 41,000 megatonnes. Use the megatonne-to-gigatonne converter for that next step up.
No. Scaling a mass by 1,000 doesn’t depend on which gas it is, so the kilotonne-to-megatonne 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 Mt of carbon (MtC) and Mt of CO₂ differ by that factor. This converter only scales kt↔Mt of the same quantity. If your source is in carbon, convert to CO₂ first with the carbon-to-CO₂ converter.