# Scientific Calculator fx-991 — Step-by-step Math Solver

> Advanced scientific calculator with step-by-step solutions, graphing, and formula library. (iPhone/iPad app by Dinh Phuc.)

- Source: https://appshunter.io/ios/app/scientific-calculator-fx-991/id1673640297 (this page in markdown: same URL + `.md`)
- Developer: [Dinh Phuc](https://appshunter.io/developer/1673640299)
- Category: Education
- Price: Free with in-app purchases
- Rating: 4.50/5 from 391 App Store ratings · 66 written reviews indexed
- Age rating: 4+
- Requires: iOS 15.0 · 26 MB
- Languages: American English, Afrikaans, Albanian, Arabic, Armenian, Azerbaijani, Basque, Belarusian, Bulgarian, Catalan and 50 more
- Released: 2023-02-28
- Data updated: 2026-08-25
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/scientific-calculator-fx-991/id1673640297/reviews.md

## What is Scientific Calculator fx?

Scientific Calculator fx-991 – The Ultimate Math & Science Tool!
Struggling with math problems, equations, or integrals?  Need a powerful scientific calculator to solve step-by-step?

With Scientific Calculator fx-991, you can calculate, graph, and find formulas instantly – making learning math, physics, and chemistry easier than ever! 

Key Features
+ Step-by-step equation solver – Enter any equation and get a detailed step-by-step solution.
+ Advanced scientific functions – Solve fractions, algebra, derivatives, integrals, trigonometry, and more.
+ Graphing mode – Visualize mathematical functions interactively.
+ Extensive formula library – Access key formulas for math, physics, and chemistry in seconds.
+ Unit converter – Quickly convert between different measurement units.
+ Casio fx-991 inspired interface – A familiar and intuitive experience for students.

 Perfect for high school and college students, engineers, and professionals in STEM fields!

 Who is this app for?
High school students – Solve algebra, calculus, and physics problems efficiently.
 College & university students – Master engineering, physics, and complex math subjects.
 STEM professionals – Perform advanced calculations quickly and accurately.

 Download Scientific Calculator fx-991 now and simplify your calculations! 
Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/.

## Key features

- Step-by-step equation solver
- Advanced scientific functions
- Graphing mode
- Formula library
- Unit converter
- Casio fx-991 inspired interface

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Monthly Premium Access | $1.99 | per month |
| Yearly Premium Access | $7.99 | per year |
| 6-Month Premium Membership | $2.49 | per 6 months |

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Remove Ads 30 Days | $0.99 | one-time |
| HiEdu Pro Lifetime | $14.99 | one-time |


## Recent user reviews (10 of 66)

All indexed reviews: https://appshunter.io/ios/app/scientific-calculator-fx-991/id1673640297/reviews.md

### 5/5 — Very useful and no problems with this app 🙂

*2026-08-19*

I can’t think of any bad things about this app and I also love how it has imaginary numbers like i

**Developer response:** We truly appreciate your support! 🙌 Your 5-star rating means a lot to us. Keep enjoying HiEdu, and don’t forget to recommend it to your friends! 🎉

### 5/5 — I love this, good stuff ☝️🤓

*2026-06-12*

I love this, good stuff ☝️🤓

**Developer response:** Amazing! Thank you for the 5-star review! 💖 We are so happy to know that you are satisfied with the app. If you have any suggestions to make it even better, feel free to share! 😊

### 5/5 — Really awesome

*2026-06-10*

Super easy to use and free!!

**Developer response:** Thank you so much for your 5-star rating! 🌟 Your support is a great motivation for us to continue developing and improving the app. We wish you a fantastic experience with HiEdu! 🚀

### 4/5 — Reseña de Marcus

*2026-06-08*

Es la aplicación más curada y útil me llamo marcushh el ora aya tata

**Developer response:** ¡Hola Marcus! 😊 Muchas gracias por tu reseña y tus amables palabras. Nos alegra mucho saber que consideras nuestra aplicación útil y bien cuidada. Seguiremos trabajando para ofrecer la mejor experiencia posible. ¡Gracias por tu apoyo! 🙏

### 5/5 — Rev

*2026-06-03*

Quite fast and easy to use

**Developer response:** Amazing! Thank you for the 5-star review! 💖 We are so happy to know that you are satisfied with the app. If you have any suggestions to make it even better, feel free to share! 😊

### 5/5 — 공학용계산 잘 됨

*2026-05-25*

복소수 계산 주로 사용중

**Developer response:** 별 5개 평점을 주셔서 정말 감사합니다! 🌟 여러분의 응원은 저희가 앱을 계속 개발하고 개선하는 데 큰 동기가 됩니다. HiEdu와 함께 즐거운 시간을 보내시길 바랍니다! 🚀

### 5/5 — Good app

*2026-05-24*

Very very very helpful exactly like my physical Casio and so helpful

**Developer response:** Amazing! Thank you for the 5-star review! 💖 We are so happy to know that you are satisfied with the app. If you have any suggestions to make it even better, feel free to share! 😊

### 5/5 — 너무 좋네요

*2026-05-20*

완벽합니다

**Developer response:** 별 5개 평점을 주셔서 정말 감사합니다! 🌟 여러분의 응원은 저희가 앱을 계속 개발하고 개선하는 데 큰 동기가 됩니다. HiEdu와 함께 즐거운 시간을 보내시길 바랍니다! 🚀

### 5/5 — 정말 좋은 계산기

*2026-05-19*

카시오 fx-fx570es plus & fx-570cw 두종류를 사용하고 있어 비슷한 디자인과 기능이라 정말 편리합니다.

**Developer response:** 정말 멋집니다! 별 5개 리뷰 감사합니다! 💖 앱에 만족하셨다니 정말 기쁩니다. 더 나은 앱을 만들기 위한 의견이 있으시면 언제든지 알려주세요! 😊

### 5/5 — 🫶

*2026-05-19*

🥰

**Developer response:** Thank you so much for your 5-star rating! 🌟 Your support is a great motivation for us to continue developing and improving the app. We wish you a fantastic experience with HiEdu! 🚀

## Frequently asked questions about Scientific Calculator fx

### What does the Scientific Calculator fx-991 app do?

This app functions as a powerful scientific calculator designed to help users solve math and science problems. It offers step-by-step solutions for equations, advanced mathematical functions, interactive graphing, an extensive formula library, and a unit converter.

### What are the key features of this calculator app?

Key features include a step-by-step equation solver, advanced scientific functions for algebra and calculus, a graphing mode to visualize functions, a comprehensive formula library for math, physics, and chemistry, and a unit converter. It also boasts an interface inspired by the Casio fx-991.

### Is this app free to use?

The app is available for free download and use, but it does contain in-app purchases and advertisements. Users may choose to purchase additional features or remove ads through these in-app options.

### Who would benefit from using this app?

This app is ideal for high school and college students studying math, physics, and chemistry, as well as engineers and professionals in STEM fields. Its comprehensive features and step-by-step solutions make complex calculations and learning more accessible.

### What kind of math problems can this calculator solve?

The calculator can handle a wide range of math problems, including algebra, fractions, trigonometry, derivatives, and integrals. It provides detailed step-by-step solutions to help users understand the problem-solving process.

## Version history (last 5 releases)

### 1.9.0 — 2026-08-21

◆ Enhanced derivative feature: now supports finding the derivative expression of a function, in addition to calculating the derivative value at a specific point.
◆ Performance improvements and bug fixes.

### 1.8.9 — 2026-07-25

∙ More detailed step-by-step solutions for equations and inequalities.
∙ Added mathematical concepts, solution steps, answer verification, and similar practice exercises. 
∙ Performance improvements and bug fixes.

### 1.8.8 — 2026-05-23

Optimize speed and detailed results when solving quadratic equations, fractional equations, and rational equations.

### 1.8.5 — 2026-05-18

• Improved accuracy of integral calculations for better results 
• Fixed edge cases in numerical integration

### 1.8.4 — 2026-05-14

∙ Improved and optimized search results when users look up formulas and knowledge.

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## More apps by Dinh Phuc

- [HiEdu Formula Master Global](https://appshunter.io/ios/app/hiedu-formula-master-global/id6475017034)
- [Scientific Calculator He-36X](https://appshunter.io/ios/app/scientific-calculator-he-36x/id6475181957)
- [2000 Common English Sentences](https://appshunter.io/ios/app/2000-common-english-sentences/id6476976197)
- [Calculator For Kids](https://appshunter.io/ios/app/calculator-for-kids/id6503827281)
- [Math Genius - Grade 1](https://appshunter.io/ios/app/math-genius-grade-1/id6547847892)

All apps by Dinh Phuc: https://appshunter.io/developer/1673640299

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-25.*