Mental Maths: Estimation Tricks Kids Can Learn in a Week

Estimation stops “wild answers”. It’s the skill that helps a child notice, “Wait… that can’t be right,” before they hand in the work.

In just a week, you can build a simple habit: get a sensible range first, then do the exact calculation.

Related guides: Maths (7–11) · 11+ Prep · Study Skills & Focus · All blog posts

Who this is for

• Kids aged 7–11 who get the method right but the answer is “obviously wrong.”
• Kids who rush and don’t notice mistakes until it’s too late.
• Parents/tutors who want a quick checking routine that actually sticks.

Why estimation matters (more than people think)

• It catches errors early. Wrong operation? Wrong unit? Place value slip? Estimation flags it.
• It builds number sense. Kids stop treating numbers like random symbols.
• It reduces anxiety. When a child has an expected range, they feel more in control.

Core habits (keep these simple)

• Round first, then adjust. Make the numbers easy, then nudge closer if needed.
• Check units. Pounds vs pence, minutes vs hours, cm vs m — units catch lots of mistakes.
• Ask: “Should the answer be bigger or smaller?”
• Use a range, not one number. “Around 200” is better than “exactly 198” for an estimate.

Mini examples you can say out loud

• 49 + 52 ≈ 50 + 50 = 100 (so the exact answer should be near 100).
• 19 × 6 ≈ 20 × 6 = 120 (so 12 is impossible; 120-ish makes sense).
• £3.50 × 4 is around £12–£16 (so £140 is a unit/place value error).

A 7-day mini plan

10–15 minutes a day is enough. The goal is consistency, not long sessions.

• Day 1–2: rounding (to 10, 100, 1 decimal place — whatever fits the level)
• Day 3–4: estimating sums and products (add/multiply using rounded numbers)
• Day 5: checking answers (does the exact answer sit near the estimate?)
• Day 6: word problems with estimation first (predict, then solve)
• Day 7: mixed review (rounding + estimating + checking)

How to teach it (one sentence)

Before they solve, say:

“Give me a sensible range first — then do the exact maths.”

This trains the habit that prevents silly errors under pressure.

Try this next

Before solving, ask for an answer range:

• “Is it about 20 or about 200?”
• “Should it be between 30–40 or 300–400?”
• “Is it closer to 1, 10, or 100?”

If the final answer lands far outside the range, something went wrong — and you catch it early.

If your child also struggles with rushing/misreading, pair this with: How to Stop Careless Mistakes and Word Problems: The 4-Step Method.

Want a low-friction way to practise this daily? Use the free Classroom Trial and make “estimate first” the rule before every maths question.