Unit errors are among the easiest marks to lose and the easiest to prevent. Writing units at every step turns them from an afterthought into a check.
Two different failures
The first is omission — a correct number with no unit, which is an incomplete answer and is marked as such.
The second is conversion, where the arithmetic is right but the quantities were in different units. That one changes the answer rather than just its presentation.
Why conversions go wrong
The direction is guessed. Converting to a smaller unit always produces a larger number, and students who do not check the direction are right half the time.
The factor is misremembered. Metres to centimetres is a hundred; kilometres to metres and kilograms to grams are a thousand, and mixing them up is common.
Conversion is forgotten entirely when the question mixes units — a length in metres and another in centimetres, added directly.
Habits that prevent both
Write the unit at every step, not just on the final answer. It makes a mismatch visible before it becomes an error.
Convert everything to a single unit at the start of a question, before any calculation. Doing it as you go is where the mistakes happen.
Ask whether the answer should be a bigger or smaller number before converting. That single question prevents most directional errors.
A routine that prevents most unit errors:
- Read the question and note every unit used
- Convert everything to one unit before calculating
- Write the unit on every line of working
- Check the direction: smaller unit means bigger number
- Confirm the final unit matches what was asked for
Area and volume are the hard cases
Converting area and volume units is not the same as converting length. Students who divide by a hundred to convert cm² to m² are applying the length factor to an area.
Where a syllabus excludes those conversions, as the primary one does, it is worth knowing so a child is not attempting something they have not been taught.
What lessons at Odyssey are actually like
Here is a student talking about what studying with us is actually like. She is at secondary level; the teaching method is the one we use throughout, adjusted to the age. More are on Odyssey Math TV.
Where Odyssey fits
We mark for units in class from primary level onwards, because the habit has to be automatic before it will survive an exam.
We teach maths only, in small classes at Hexacube, 160 Changi Road #01-02, about three minutes from Eunos MRT. See the primary and secondary programmes, our MOE-aligned curriculum, schedules and fees, or the tutors who teach. Free video solutions to past-year papers are on Odyssey Math TV.
A weakness at this stage rarely announces itself. It surfaces a year or two later wearing a different name, which is why parents so often report that the trouble “started” in a year where it merely became visible. Teaching Primary 1 through Primary 6 on one curriculum is what makes tracing it back to the real starting point practical rather than speculative.
Come and sit in on a lesson before deciding anything. The first one is free and its purpose is diagnostic: we want to know what your child can actually do, not what a report card says. Arrange a free trial or WhatsApp +65 8512 6882.
What we describe here comes from teaching this syllabus in our own classes since 2012. It is not a forecast for any individual child: progress is produced jointly, by a student willing to do the work with support at home. We do not promise grades. Topics follow the MOE primary mathematics syllabus — check the current syllabus on the MOE website for the definitive version, and see our curriculum page for how we teach it.
Frequently asked questions
Do students really lose marks for missing units?
Yes, routinely. An answer to a measurement question is incomplete without its unit.
How do I stop my child converting the wrong way?
Ask whether the answer should be bigger or smaller first. Smaller units always give bigger numbers.
Why are area conversions harder?
Because the factor is squared. Converting cm² to m² is not the same as converting cm to m, and applying the length factor is a common error.
When should conversion happen in a question?
At the start, before any calculation. Converting partway through is where most mistakes occur.
