For GCSE, A-level, AP, IB and SAT maths
Find the line that costs you marks.
Solve it on paper, snap a photo, and see which line would lose marks. A hint, never the answer.
Free in the beta. No account. Photos deleted after marking.
85 of 100
planted mistakes found in 289 real handwritten solutions it had never seen.
Our own test on the FERMAT research dataset, November 2026, graded straight from the photo. It also flagged 66 of 189 solutions the dataset marks as correct. Some of those contain real slips, some are its own mistakes, so every flag comes with a reason you can check.
Can you spot the mistake?
Three made-up examples, marked the way Grid & Pen marks your own work. Pick the line you think loses marks.
Solve 3(x − 2) + 4 = 2x + 7
Tap the line you think loses marks.
Made-up examples. On your own work, every line gets checked like this.
How it works
Solve it on paper
Work it out by hand, the way you will in the exam.
Take a photo
Check that we read your writing right. You can fix any line before it’s marked.
See where marks go
Each line gets a tick, a cross or a warning, with a hint that points to the mistake.
Answer apps give you the answer. Exams mark your working.
Most of the marks in a maths exam are for method. Grid & Pen doesn’t solve the problem for you. It reads what you wrote and shows which step would lose marks, so you can fix the habit before exam day.
| Answer apps | Tutor | Grid & Pen | |
|---|---|---|---|
| Built to check your own handwritten working | No | Yes | Yes |
| Shows which line loses marks | No | Yes | Yes |
| Gives a hint instead of the answer | No | Yes | Yes |
| Trains you for a paper exam | No | Yes | Yes |
| Any time, in seconds | Yes | No | Yes |
| Cost | Free or monthly | Paid by the hour | Free in the beta |
Answer apps: apps that scan a question and show the worked solution.
Questions
Feedback comes from an AI, not a teacher. Check it like you’d check a friend’s answer.
Is it free?
Yes, during the beta. You get a few checks a day.
Which topics?
Algebra, equations, functions and calculus first. More topics come during the beta.
What happens to my photo?
It’s deleted as soon as your work is marked. You don’t need an account.
Can it get things wrong?
Yes, it’s an AI. That’s why you confirm what it read before anything is marked, and why every hint tells you where to look instead of what to write. In our test it also flagged some correct solutions, mostly for skipped steps.