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Primary - Stage 3 (Year 5 & 6) Stage 3 (Year 5 & 6) Mass

Convert between metric units of mass - kg & t

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Theory

One tonne is \(1000\) kilograms. To change tonnes to kilograms, multiply by \(1000\); to change kilograms to tonnes, divide by \(1000\).

A kilogram (kg) and a tonne (t) are metric units of mass. A tonne is used for very heavy masses, and \(1\text{ t} = 1000\text{ kg}\).

To change tonnes to kilograms, multiply by \(1000\). A kilogram is smaller, so the number gets bigger.

To change kilograms to tonnes, divide by \(1000\). A tonne is larger, so the number gets smaller. A mixed mass like \(3\) t \(250\) kg is added once both parts are in the same unit.

\(1\text{ t} = 1000\text{ kg}\). This one fact drives every conversion between kilograms and tonnes.
Converting between kilograms and tonnes Kilograms to tonnes divides by 1000; tonnes to kilograms multiplies by 1000. kgt ÷1000 ×1000
To a smaller unit (t \(\rightarrow\) kg), \(\times 1000\); to a larger unit (kg \(\rightarrow\) t), \(\div 1000\). For example \(3\text{ t} = 3000\text{ kg}\).

Every step multiplies or divides by \(1000\).

TonnesKilograms
\(1\) t\(1000\) kg
\(2.5\) t\(2500\) kg
\(0.75\) t\(750\) kg
\(0.5\) t\(500\) kg
\(4\) t\(4000\) kg

Converting kilograms and tonnes

  1. Decide the direction: which unit are you changing to?
  2. To kilograms (the smaller unit), multiply by \(1000\).
  3. To tonnes (the larger unit), divide by \(1000\).
  4. Mixed mass? Change the tonnes part to kilograms, then add the kilograms.
Example 1 — Tonnes to kilograms
How many kilograms are in \(3\) t?
Solution

A kilogram is smaller, so multiply.

\(3 \times 1000\)\(=\)\(3000\)

So \(3\text{ t} = 3000\) kg.

Example 2 — Kilograms to tonnes
Write \(5000\) kg in tonnes.
Solution

A tonne is larger, so divide.

\(5000 \div 1000\)\(=\)\(5\)

So \(5000\text{ kg} = 5\) t.

Example 3 — A decimal answer
Write \(2500\) kg in tonnes.
Solution

Divide by \(1000\).

\(2500 \div 1000\)\(=\)\(2.5\)

So \(2500\text{ kg} = 2.5\) t.

Example 4 — A mixed mass
Write \(3\) t \(250\) kg in kilograms.
Solution

Change the tonnes to kilograms, then add.

\(3000 + 250\)\(=\)\(3250\)

So it is \(3250\) kg.

Common pitfalls

Multiplying when you should divide. To a smaller unit the number grows, so multiply; to a larger unit it shrinks, so divide.
Using \(100\) instead of \(1000\). A tonne is a thousand kilograms, so the factor is always \(1000\).
Adding a mixed mass wrongly. \(3\) t \(250\) kg is \(3000 + 250 = 3250\) kg, not \(3025\) kg.

Frequently asked questions

How many kilograms are in a tonne?

\(1000\). A tonne is a thousand kilograms, so \(1\text{ t} = 1000\text{ kg}\).

How do I change tonnes to kilograms?

Multiply by \(1000\), because a kilogram is smaller. For example \(3\text{ t} = 3 \times 1000 = 3000\) kg.

How do I change kilograms to tonnes?

Divide by \(1000\), because a tonne is larger. For example \(5000\text{ kg} = 5000 \div 1000 = 5\) t.

What is \(2500\) kg in tonnes?

\(2.5\) t. Divide by \(1000\): \(2500 \div 1000 = 2.5\).

How do I handle a mass like \(3\) t \(250\) kg?

Change the tonnes to kilograms first, then add: \(3000 + 250 = 3250\) kg.

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