AI Grammar Checker Comparison — Grammarly vs QuillBot & more

Every value in the table is a fact taken from each vendor's own pricing and feature pages — free-tier limits, the cheapest paid plan, language count, platforms and which of five optional features each tool supports. Nothing here rates correction qualityor opinion. The only computed element is the “best match” score, and it is fully deterministic so you can check it by hand.

Choosing works in two stages. First, hard filtersremove any tool that cannot meet your requirements: each “must-have” toggle drops tools lacking that capability, and the budget selector drops tools whose cheapest paid plan exceeds your cap. Under a Free only budget the filter is stricter — a required feature must be available on the free tier, not merely exist behind a paywall. That is why asking for a plagiarism checker on a free-only budget returns nothing: none of these tools include plagiarism scanning for free.

Second, the survivors are ranked by a transparent weighted score:

• useCaseFit — a fixed 0–1 value per tool and use case, drawn from documented feature sets (QuillBot rates high for content writers because paraphrasing is its core product; LanguageTool rates high for non-native writers because it documents 30+ languages).
• freeTierGenerosity— each free tier scaled 0–1 against the most generous in the set. LanguageTool's 10,000-character free window is the benchmark at 1.0.
• priceValue — 1 − cheapestPaid / maxPaidInSet, so the cheapest plan scores near 1 and the most expensive scores 0.
• featureCoverage — the fraction of the five optional features (plagiarism, paraphrase, integration, offline, privacy) the tool supports.

Ties break by larger free tier, then lower price. Every weight and input is printed here and in the code comments, so the ranking is reproducible — the calculator even runs an independent second computation of each score to confirm the two paths agree before showing you a pick.

Each row's figures come from that vendor's own pricing or product page, cross-checked on 2026-07-08:

• Grammarly — plans & pricing
• QuillBot — Premium features & pricing
• LanguageTool — Premium & self-host
• ProWritingAid — pricing
• Ginger Software — pricing
• Microsoft Editor — free vs Microsoft 365 tiers

Grammar-tool pricing and free-tier caps change often. These were last verified on 2026-07-08; always confirm the current figure at the vendor link before you buy. Found a stale number? Email me and I'll update it.