Looking for an Astra AI alternative? For maths only, Photomath gives basic step-by-step solutions free. For any subject with a chat and voice tutor, Gauth is the closest match. For a human tutor on top of AI, Brainly. For a cheaper all-round study app with a tutor and an exam plan, Knowunity. And if what you want is to study for a test from your own notes, Synt, which we make.
A disclosure: we make Synt, so this is not a neutral list. We only state what we checked: every price and feature below comes from the apps' official US App Store listings and websites, checked on 8 November 2026.
First, what Astra AI does
Astra AI (4.8 stars from about 5,600 ratings, 38 app languages) is an AI tutor for maths, physics, chemistry and more. Its listing describes Snap and Solve, a Solver mode and a Socratic mode, lessons aligned with your country's curriculum and Exam Prep: a study plan from a photo of your exam or the topics you pick. Its website adds plans built from your notes, slides and past papers, oral exams and timed mock exams, and says "you can start free, no card required", without listing the free limits.
Astra AI Plus costs $8 a week, $24 a month or $119.99 a year in the US App Store; Sigma is $80 a month, and there are credit packs from $15 and an "Exam Pass" at $121.99. That price is the main reason people look for alternatives.
The 5 alternatives at a glance
| App | Best for | Free | Paid (US App Store) |
|---|---|---|---|
| Photomath | Maths, step by step | Basic step-by-step explanations | Photomath Plus: $5.99, $7.99 or $9.99 (periods not shown) |
| Gauth | Any subject, AI tutor with voice and whiteboard | Free download | Gauth Plus: $11.99 a month, $99.99 a year (3-day trial) |
| Brainly | Homework help with human tutors | Free download | Brainly Plus: $9.99 a month or $39.99 a year; Brainly Tutor: $29.99 a month or $95.99 a year |
| Knowunity | All-round: tutor, shared notes, exam plan | Core tools free | Knowunity Pro: $49.99 a year on the website |
| Synt | Studying for a test from your own notes | Text, links and photos, including the plan | Pro on the web: €29.99 a year |
Sources: US App Store listings of Photomath, Gauth, Brainly, Knowunity and Astra AI (description and in-app purchases), Knowunity's Pro page, astra-ai.co and synt.app's pricing page. In-app lists often include several prices for the same plan (offers, older prices); we quote the ones labelled with a period where Apple shows it.
1. Photomath: free maths steps
Photomath is made by Google and has 4.8 stars from over 730,000 ratings. You scan a maths problem, handwritten, printed or on screen, and get the solution broken into steps, including word problems and animated steps. Its listing says basic step-by-step explanations come at no charge.
Better than Astra AI for: maths homework on a budget. Worse for: anything that isn't maths; there's no exam plan or tutor chat across subjects.
2. Gauth: the closest all-subject tutor
Gauth has 4.8 stars from over 1.5 million ratings. Its listing describes step-by-step guidance across subjects, an AI Live Tutor by voice with a virtual whiteboard, a "study converter" that turns notes, audio or lecture links into quizzes and flashcards, and a DeepThinking mode.
Better than Astra AI for: a voice tutor that draws on a whiteboard, and a cheaper year ($99.99 vs $119.99). Worse for: Astra's curriculum-by-country lessons and oral mock exams aren't in Gauth's listing.
3. Brainly: when you want a human
Brainly (4.7 stars from about 284,000 ratings) now sells itself to parents: one-on-one help from real, qualified tutors backed by AI, homework help from a photo, test prep and maths support, with a 30-day money-back guarantee.
Better than Astra AI for: a real person checking the work. Worse for: price if you want the tutor plan ($29.99 a month), and it's aimed at K-12.
4. Knowunity: cheaper, broader
Knowunity (4.7 stars from about 12,500 ratings, 20 languages) has a chat tutor with a voice mode and step-by-step help from a photo, but its centre is a day-by-day exam plan around your test date and class timetable, with flashcards, quizzes, summaries, mock exams and over a million shared notes.
Better than Astra AI for: price ($49.99 a year on the website) and shared notes. Worse for: Astra's Socratic mode and curriculum lessons. We compared the two in detail in Knowunity vs Astra AI.
5. Synt: a plan built only from your notes
This one is ours. Synt doesn't solve homework. It takes your notes (pasted text, a link or photos of your pages) and generates a summary, a 20-question quiz, flashcards and a concept map from that material only. Give it your exam date and target grade and it plans short sessions up to the day, brings back the questions you got wrong (reworded) and puts a mock exam the day before.
On the web, the free plan covers pasted text, links and photos, including the study plan. PDF upload and YouTube are Pro, at €4.99 a week, €9.99 a month or €29.99 a year, with a 3-day trial; App Store prices are set per country.
Better than Astra AI for: subjects you study from notes (history, biology, law, languages) and a much lower price. Worse for: maths and physics problems: there's no solver and no tutor chat. Try the notes to quiz tool without an account, or the practice test generator.
Which one to choose
Stuck on maths and want it free: Photomath.
Want Astra's tutor experience for less: Gauth.
Want a real person: Brainly Tutor.
Want a tutor plus a plan and shared notes: Knowunity.
Have notes and a test date, and the subject is about understanding and remembering: Synt.
Also compared: Astra AI vs Gizmo and apps like Knowunity.
Astra AI alternatives: FAQ
Is there a free alternative to Astra AI?
For maths, Photomath gives basic step-by-step explanations at no charge. Knowunity says its core tools are free, and Synt's free plan on the web covers text, links, photos and the study plan. Gauth and Brainly are free to download and sell paid plans (Gauth Plus, Brainly Plus and Brainly Tutor).
How much does Astra AI cost?
In the US App Store (checked 8 November 2026), Astra AI Plus is $8 a week, $24 a month or $119.99 a year; Sigma is $80 a month. There are also credit packs from $15 and an Exam Pass at $121.99.
What is the best app like Astra AI for maths?
For solving and explaining maths problems step by step, Photomath and Gauth are the closest. Photomath is maths only; Gauth covers other subjects and adds a voice tutor.
Is Astra AI better than Knowunity?
Astra AI is stronger as a tutor (Socratic mode, curriculum lessons, oral mock exams). Knowunity is cheaper and adds shared notes and a plan around your timetable. See Knowunity vs Astra AI.
