A LITTLE PRACTICE, EVERY DAY·GCSE MATHS
AQA·Edexcel·OCR|Foundation + Higher
🔢
Number · Foundation & Higher

Estimation

Estimation means rounding every number to 1 significant figure, then doing a quick mental calculation to check that a more complex answer is sensible.

Put your revision into practice

Choose a topic and try a short quiz with instant explanations. Free, with no signup.

Choose a free quizFind a worked example

Revising estimation the night before an exam? These are condensed revision notes — the facts, formulas and mistakes examiners actually mark, with no long explanations. Prefer a full walkthrough with step-by-step reasoning instead? Search “Estimation GCSE” on the site for the complete guide.

🔑

Key facts to remember

  • 1To estimate, round every number in the calculation to 1 significant figure.
  • 2Use the symbol ≈ (approximately equal to), not =.
  • 3Estimates give you a sanity check for calculator answers.
  • 4For division, estimate numerator and denominator separately first.
✍️

Worked examples

Example 1

Estimate the value of (48.3 × 2.95) / 0.197.

Working

  1. Round each to 1 sf: 48.3 ≈ 50, 2.95 ≈ 3, 0.197 ≈ 0.2
  2. (50 × 3) / 0.2 = 150 / 0.2
  3. 150 / 0.2 = 750
Answer≈ 750
⚠️

Common mistakes

✗Using more than 1 sf and making arithmetic harder.
✗Rounding 0.197 down to 0 instead of 0.2 — cannot divide by 0.
✗Forgetting to use ≈ instead of =.
🎯

Exam tips

✓Always round every number to 1 sf first.
✓After estimating, compare with a given answer to decide if it is reasonable.
✓Show your rounded values before the final calculation.

Ready to test yourself on Estimation?

Get AI-marked practice questions on exactly this subtopic.

Practice this topic →
← All topicsDashboard

▶️ Watch on YouTube

Free video lessons

Click a topic to search

▶estimation GCSE maths▶estimating calculations GCSE▶rounding to 1 sf estimate▶approximation GCSE maths

Opens YouTube — pick any free GCSE video.