How to Convert a Score Into a Percentage

What It Means to Convert a Score

A score such as 17 out of 25 is hard to compare with 41 out of 50, because the totals differ. Converting both to percentages puts them on the same scale of 0 to 100, so you can see which is better, add them to other results or report them in a standard form. The idea is simple: express the score as a share of the total, then scale that share to 100.

The Formula

The total is the maximum score available, not the pass mark. If your score is a fraction, such as 17/25, it is already score over total.

Step-by-Step Example

You score 17 out of 25.

1. Divide by the total: 17 ÷ 25 = 0.68.
2. Multiply by 100: 0.68 × 100 = 68%.

For a quick check, 25 goes into 100 four times, so a score out of 25 is multiplied by 4. Here 17 × 4 = 68. The same trick works for other totals that divide into 100.

Common Totals at a Glance

Comparing Scores Out of Different Totals

Which is better, 17 out of 20 or 41 out of 50? Convert both: 17 ÷ 20 = 85% and 41 ÷ 50 = 82%, so the first is better. Always convert before comparing. Raw scores can be misleading, because a higher number does not mean a higher percentage when the totals differ. One caution is that percentages from different tests are only fairly comparable if the tests were similarly difficult.

Rescaling a Score to a New Total

Sometimes you need a score on a different scale, for example when a mark out of 25 has to be reported out of 40. Convert to a decimal, then multiply by the new total:

For 17 out of 25, the decimal is 0.68, so out of 40 the score is 0.68 × 40 = 27.2. Out of 20 it is 0.68 × 20 = 13.6, and out of 100 it is 68. The percentage itself stays the same at 68%, which is why rescaling and converting to a percentage are the same idea.

Negative Marking

Some tests subtract marks for wrong answers. Calculate the net score first, then convert. Suppose a test has 60 questions, with +1 for a correct answer and −0.25 for a wrong one. You answer 40 correctly, 12 wrongly and leave 8 blank. Your net score is 40 − (12 × 0.25) = 40 − 3 = 37. Divide by the total available, which is 60: 37 ÷ 60 = 61.67%. Blank answers score nothing but cost nothing, so they do not change the net score.

Bonus Marks and Scores Above 100%

If bonus marks take you past the total, the percentage can exceed 100. A score of 54 out of 50 is 54 ÷ 50 = 1.08, or 108%. Some institutions cap scores at 100%, and others allow the higher figure, so check your rules before you report it. Add bonus marks to the score first, then divide by the original total.

Ratings and Scores Out of 10 or 5

The same method works for ratings. A score of 7.5 out of 10 is 75%, and 4 out of 5 is 80%. Be careful when comparing a rating scale with an exam score, because they measure different things, and a rating of 4 out of 5 is not necessarily the same standard as 80% on an exam.

Converting a Percentage Back Into a Score

To go the other way, turn the percentage into a decimal and multiply by the total. A result of 68% on a test out of 40 is 0.68 × 40 = 27.2 marks. A result of 72% on a test out of 25 is 0.72 × 25 = 18 marks. This is useful when you know the percentage you want and need to know how many marks it takes, which is the idea behind our guide on calculating your exam percentage.

Rounding Scores

Keep the decimals while you calculate and round only the final answer. Check whether your institution rounds to a whole number, one decimal place or two, and whether it rounds up at a boundary. A score of 69.6% might be reported as 70%, or left as 69.6%, depending on the rule, and that can change a grade band. If the result is close to a boundary, find out how it is handled.

Adding Up Scores From Several Parts

A paper often has several sections. Suppose Part A is 18 out of 25, Part B is 31 out of 40 and Part C is 12 out of 15. The total is 18 + 31 + 12 = 61 out of 25 + 40 + 15 = 80, which is 61 ÷ 80 = 76.25%. If you instead average the three section percentages, 72%, 77.5% and 80%, you get 76.5%. The answers differ because the sections have different totals, so use the pooled method unless your institution says each section counts equally.

Converting Fractions and Decimals

You will also meet scores written as fractions or decimals. A fraction of 3/8 is 0.375, which is 37.5%. A decimal of 0.62 is 62%. The fraction 7/20 is 35% and 5/8 is 62.5%. To convert, divide the top by the bottom, then multiply by 100. To go from a percentage back to a decimal, divide by 100, which is just moving the decimal point two places to the left.

Letter Grades Are Not Percentages

A letter grade is a band of percentages, not a single number, so you cannot convert a B back into an exact percentage. Use your institution’s table for the range, and treat any single value you pick, such as the midpoint of the band, as an estimate. When you need a precise figure, use the original score instead of the letter.

Common Mistakes to Avoid

• Dividing by the pass mark. Always divide by the total available.
• Comparing raw scores out of different totals. Convert to percentages first.
• Ignoring negative marking. Work out the net score before converting.
• Forgetting to multiply by 100. A result of 0.68 is not 0.68%.
• Rounding too early. Round only the final answer.

Conclusion

To convert a score to a percentage, divide by the total and multiply by 100. The same idea lets you compare scores from different totals, rescale a mark to a new total and convert a percentage back into marks. When a test has negative marking or bonus marks, adjust the score first, then convert.