Knackpad

Answer Sheet Grader

Upload quiz photos, enter your answer key — get scores, letter grades, and class analytics instantly. On-device AI, no data leaves your browser.

Grades instantly Up to 100 questions FERPA / GDPR safe No sign-up
1
Upload Answer Sheets

One photo per student. Clear lighting, flat paper, answers circled or written in large print works best. JPG, PNG, WebP, HEIC — any orientation.

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Click to browse or drag & drop images here
Multiple files OK — one photo per student
2
Enter Your Answer Key

Correct answers in order, one per question. Case-insensitive. Supports A/B/C/D, True/False, numbers, or short words.

Or paste all answers (one per line):

Paste auto-sets the question count to match the number of lines.

3
Grading Options

Customize how scores and letter grades are calculated.

Grading scale
Score curve (add points)
Points per correct answer
Negative marking (per wrong)
4
Grade
AI model not loaded. Click "Load AI Model" to prepare (first time only — ~300 MB, cached).
First load only: The SmolVLM-256M AI model downloads from HuggingFace and caches in your browser. Subsequent visits are instant and fully offline.
How it works

This tool uses SmolVLM-256M-Instruct, a compact vision-language model from HuggingFace, running entirely inside your browser via Transformers.js with WebGPU or WASM acceleration. Your images are never sent to any server.

  1. Upload one photo per student. The sheet should show answers written, circled, or bubbled clearly. Good lighting, flat paper, and large handwriting get the best read rate.
  2. Enter your key — the correct answers in order. Use the quick presets (10/20/25/30/40/50 questions) or paste a plain-text list.
  3. Set grading options — choose a letter-grade scale, add a curve, set per-question point values, or enable negative marking for penalty scoring.
  4. Load the AI model (~300 MB, cached after first load, works offline). The model reads each student's answers via a structured vision prompt.
  5. Grade — each sheet is processed and compared to your key. AI reads are cached per session, so re-grading with a corrected key or changed curve is instant.
  6. Export the full score table (with letter grades, raw answers, and per-question correctness) as CSV, or print directly.

Tip for best accuracy: flat paper, good lighting, and clearly written/circled single-character answers (A/B/C/D) yield the highest read rate. Any answer the model marks as ? should be verified manually — re-run individual sheets by removing and re-uploading after improving the photo.

Frequently asked questions
Does this tool upload my students' answer sheets to a server?
No. Every image and answer is processed locally inside your browser using WebGPU or WASM. Nothing ever leaves your device. This makes the grader safe to use with student work, even under FERPA (USA) or GDPR (EU) constraints.
What kinds of answer sheets does it support?
It works best with clear single-character or short-word answers — multiple-choice letters (A, B, C, D), True/False, numbered answers (1, 2, 3), and short words (e.g. "Paris", "photosynthesis"). Standardized bubble-fill sheets (like Scantron) work when the bubbles are darkly and fully filled. Complex diagrams, multi-line essays, or very faint pencil marks are outside this tool's scope.
What do the grading options do?
Grading scale sets the A/B/C/D/F percentage thresholds. Score curve adds a flat number of percentage points to every student's final score (useful if you want to bump a class up). Points per correct answer lets you weight each question (e.g. 2 points each gives a 50-question test a 100-point scale). Negative marking subtracts points for wrong answers — common in competitive exams and standardized tests.
Why does the model sometimes read "?" for an answer?
The AI may be uncertain when a mark is unclear — faint pencil, crossed-out answers, smudges, or extreme glare. When you see ? in the table, check that question manually. By default, ? answers are treated as skipped (not wrong) — check "Count unread answers as wrong" to change this.
Can I re-grade after fixing my answer key or changing a curve?
Yes, and it is instant. The AI's raw reads are cached for the entire browser session. Just edit any key field, change the curve or scale, and click "Grade All Sheets" again — no AI inference runs again unless you add new photos.
How many questions and students can I grade?
Up to 100 questions per sheet, unlimited students. Processing takes roughly 5–20 seconds per sheet depending on your device's GPU. For large classes (30+), let the model load fully before adding photos, and consider batching in groups of 20–25.