How to use this calculator
- Enter or choose total questions.
- Enter or choose questions attempted.
- Enter or choose correct answers.
- Enter or choose marks for a correct answer.
- Enter or choose marks deducted for a wrong answer.
- The score updates as you type. Use Copy result or Share to keep it.
Method
Score = Correct × M+ − (Attempted − Correct) × M−; Guess value = M+ ÷ k − M− × (k − 1) ÷ k; Break-even accuracy = M− ÷ (M+ + M−)
- M+
- marks for a correct answer
- M−
- marks deducted for a wrong answer
- k
- answer choices per question
Worked example
- Wrong = 80 − 60 = 20; score = 60 × 4 − 20 × 1 = 220 of 400 (55%).
- A blind guess among 4: 1/4 × 4 − 3/4 × 1 = +0.25 marks on average.
- Break-even accuracy = 1 ÷ (4 + 1) = 20%.
60 right and 20 wrong under +4/−1 marking scores 220 of 400; even a blind guess gains 0.25 marks on average.
What the result means
If you can rule out even one option, your chance of being right rises and guessing becomes more worthwhile. Answer whenever your confidence is above the break-even accuracy.
Assumptions and limits
- Each question has exactly one correct option and unattempted questions score zero.
- Sections with different marking schemes need to be calculated separately and added.
Questions
Should I guess with negative marking?
Guess when your chance of being right is above M− ÷ (M+ + M−). With +4/−1 that is 20%, so a blind guess among four options (25%) just pays off.
What does accuracy mean here?
Correct answers as a share of questions you attempted, which shows how careful your attempts were.