"How many kg in a ton" is typed in the UK about 4,000 times a month, with "how many kg in a tonne" another 1,400, and the honest answer begins with a question back: which ton? There are three in use, and they differ by up to 12 percent. This page settles which is which, then gives the whole mass chart from milligrams to tonnes and from ounces to tons, using the exact factors from the US National Institute of Standards and Technology (NIST Special Publication 811, Appendix B), and ends with a printable chart and practice questions, because converting between g, kg and tonnes is a Year 5 and 6 objective in England, a Year 5 and 6 one in Australia, and a Grade 4 and 5 standard in the US.
Download the mass conversion chart with practice (PDF) (A4, the metric and imperial charts on page 1, the practice set with answers on page 2, free).
The three tons
| Name | Defined as | In kilograms | Where it is used |
|---|---|---|---|
| Metric ton (tonne, t) | 1,000 kg exactly | 1,000 kg | UK, Australia, NZ, Canada, India, EU, science everywhere |
| Short ton (US ton) | 2,000 lb | 907.18 kg | United States (trucks, coal, "a ton of bricks") |
| Long ton (imperial ton) | 2,240 lb | 1,016.05 kg | Old British unit; still used for ships' displacement |
So "how many kg in a ton" is 1,000 in a British, Australian, Canadian or Indian classroom and 907 in an American one. The UK legally adopted the tonne for trade decades ago; the word "ton" survives in speech ("weighs a ton") and in the long ton for shipping. Exam boards write "tonne" or "t" when they mean the metric one, and that is the only ton on a GCSE, NAPLAN or CBSE paper.
The metric chart: milligram to tonne
| Unit | Symbol | Equals |
|---|---|---|
| 1 tonne | t | 1,000 kg = 1,000,000 g |
| 1 kilogram | kg | 1,000 g = 1,000,000 mg |
| 1 gram | g | 1,000 mg |
| 1 milligram | mg | 1,000 micrograms (µg) |
Each step is a thousand, so every metric mass conversion is "move the decimal point three places". Big unit to small unit, the number gets bigger (multiply): 2.5 kg = 2,500 g. Small unit to big, the number gets smaller (divide): 750 g = 0.75 kg.
- 1 kg = 1,000 g, so 3.2 kg = 3,200 g and 450 g = 0.45 kg.
- 1 t = 1,000 kg, so 2.4 t = 2,400 kg and 650 kg = 0.65 t.
- 1 g = 1,000 mg, so a 500 mg tablet is 0.5 g and 0.0005 kg.
A worked example of the Year 6 and Grade 5 kind: a lorry can carry 3.5 tonnes. It is loaded with 1,800 kg of sand and 1,250 kg of gravel. 1,800 + 1,250 = 3,050 kg = 3.05 t, so 0.45 t (450 kg) of capacity is left.
The imperial and US chart: ounce to ton
| Unit | Equals | In metric |
|---|---|---|
| 1 ounce (oz) | 1⁄16 lb | 28.35 g |
| 1 pound (lb) | 16 oz | 453.59 g (0.4536 kg) |
| 1 stone (st) | 14 lb | 6.35 kg |
| 1 hundredweight, US (short cwt) | 100 lb | 45.36 kg |
| 1 hundredweight, UK (long cwt) | 112 lb = 8 stone | 50.80 kg |
| 1 short ton (US) | 2,000 lb = 20 short cwt | 907.18 kg |
| 1 long ton (UK) | 2,240 lb = 20 long cwt = 160 stone | 1,016.05 kg |
The pound has been exactly 0.45359237 kg in both countries since 1959, so the whole table hangs off that one number: 16 ounces to the pound, 14 pounds to the stone, 2,000 or 2,240 pounds to the ton. The ounce here is the avoirdupois ounce on a kitchen scale, not the fluid ounce in a measuring jug (see the kitchen conversion chart).
Stone: Britain's unit for people
British adults still give their body weight in stones and pounds ("11 stone 4"), and some Irish and Australian families do too. 1 stone = 14 lb = 6.35 kg. To convert: 11 stone 4 lb = 158 lb = 71.7 kg. The other way, 80 kg = 176 lb = 12 stone 8 lb. US scales read in pounds only; Australia and India in kilograms only.
Converting between the two systems
The one number to carry in your head is 1 kg = 2.2 lb (2.2046 to four places).
- kg to lb: multiply by 2.2. 25 kg of luggage = 55 lb (just over the 50 lb airline limit).
- lb to kg: divide by 2.2, or multiply by 0.454. 150 lb = 68 kg.
- Short tons to tonnes: multiply by 0.907. Tonnes to short tons: multiply by 1.102.
- Long tons to tonnes: multiply by 1.016. The long ton and the tonne are so close (1.6 percent apart) that engineers once treated them as equal.
- Ounces to grams: multiply by 28.35. A 4 oz portion is 113 g.
Which ton each country means
| Country | "Ton" in everyday speech | In school and law |
|---|---|---|
| UK | the tonne, 1,000 kg (long ton only for ships) | tonne; GCSE and SATs use t, kg, g, mg and expect "imperial units in common use" (pounds, stone, ounces) to be recognised |
| Australia, NZ, Canada | the tonne | tonne; the Australian Curriculum converts between metric units only |
| India | the tonne (also "metric ton") | tonne; CBSE Class 5 to 7 use g, kg and tonne, with the quintal (100 kg) in agriculture |
| USA | the short ton, 2,000 lb | US customary (oz, lb, ton) in Grades 4 and 5, metric alongside in science |
The quintal is worth knowing for Indian families: 1 quintal = 100 kg, so 10 quintals = 1 tonne; mandi prices are per quintal.
Where it sits in each curriculum
| Curriculum | When | What is expected |
|---|---|---|
| England | Year 5 (convert between different units of metric measure), Year 6 (convert between standard units of mass using decimal notation) | g, kg, t both ways with decimals; recognise pounds and ounces |
| Australia | Year 5 and 6 (choose and convert between appropriate metric units of mass) | g, kg, t |
| US Common Core | Grade 4 (4.MD.1 record equivalents, oz, lb, g, kg), Grade 5 (5.MD.1 convert within a system in multi-step problems) | both systems, each within itself |
| India (CBSE) | Class 4 and 5 (g and kg), Class 6 and 7 (tonne, quintal, decimals) | metric |
Practice (answers in the PDF)
- How many kilograms are in 2.5 tonnes? In 0.4 tonnes?
- A bag of rice is 5 kg. How many bags make a tonne?
- An elephant weighs 5,400 kg. How many tonnes is that? Roughly how many US short tons?
- A parcel weighs 2 lb 8 oz. What is that in kilograms?
- A man weighs 13 stone 2 lb. What is that in pounds, and in kilograms?
- Which is heavier, 1 long ton or 1 tonne? By how many kilograms?
Download the chart and the practice set (PDF)
Where to get help
A 1-on-1 online maths class with a tutor who holds a master's in mathematics and teaches KS2 and KS3, the Australian Years 4 to 8, CBSE Class 4 to 8 and US Grades 3 to 7 every week: units taught as a ladder of thousands and a handful of exact factors, with the decimal-point moves practised until they are automatic. The subjects page lists every maths course; the free 30-minute first class is a real lesson on this week's homework. The next pages in this set are the length units chart and the SI base units sheet.
Questions parents ask
1How many kg are in a ton?
2How many kg in a tonne?
3Is a ton the same as a tonne?
4How many pounds in a kg?
5How many grams in a kilogram?
See how we teach this, 1-on-1 online →
Shobha
Founder and lead tutor, Science with Shobha
Teaching maths, science and English to children online since 2018. 500+ students, 20+ tutors, families in nine countries.