# 555 Calc vs AVR Tutorial

The clearest difference is rating: AVR Tutorial at 5.0 against 555 Calc's 4.0. AVR Tutorial also leads on ads (none vs shown) and update cadence (every 3 months vs every 20 months). 555 Calc's advantage is in-app purchases (none vs 10). On price, ratings volume and device support there is nothing between them.

Both are free to download. AVR Tutorial sells 10 one-off in-app purchases. 555 Calc asks for nothing beyond the download.

AVR Tutorial holds the better App Store score, 5.0 against 4.0. Both are backed by a comparable volume of ratings — 3 and 2 respectively. Written reviews point the same way: 50% of 555 Calc's written reviews are positive against 75% of AVR Tutorial's.

555 Calc ships an update every 20 months, AVR Tutorial every 3 months. The most recent releases landed on September 27, 2026 and September 24, 2026 respectively.

## The numbers

| Metric | 555 Calc | AVR Tutorial |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [4.0 (3 ratings)](https://appshunter.io/ios/app/555-calc/id868058244/reviews) | **[5.0 (2 ratings)](https://appshunter.io/ios/app/avr-tutorial/id1070496499/reviews)** |
| Number of ratings | **3** | 2 |
| Positive reviews | 50.0% of reviews | **75.0% of reviews** |
| In-app purchases | **No** | Yes |
| Ads | Yes | **No** |
| Update frequency | Every 20 months | **Every 3 months** |
| Monetization | **Ad-supported** | Free with in-app purchases |
| Size | 18 MB | 33 MB |
| Requires iOS | 11.0 | **9.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Jibiki Works](https://appshunter.io/developer/556845808) | [Siu Yuen Ho](https://appshunter.io/developer/814088527) |

## What reviewers say

### 555 Calc

[App page](https://appshunter.io/ios/app/555-calc/id868058244)

This utility app helps engineers and hobbyists calculate resistor values for circuits using the Timer IC 555. Simply input frequency, duty ratio, and capacitor values to get the required resistor outputs.

**Highlights:** Calculate resistor values, Input frequency, Input duty ratio, Input capacitor value, Timer IC 555 circuit design

**Features:** macOS Compatibility

**In-app purchases:** none


### AVR Tutorial

[App page](https://appshunter.io/ios/app/avr-tutorial/id1070496499)

This app simplifies learning AVR microcontrollers with a code wizard that generates C source code for various peripherals. It offers demo projects and an architecture review, making complex MCU programming more accessible for hobbyists and students.

**Highlights:** AVR architecture review, AVR assembly and C language, 21 demo projects, Code wizard for peripherals, Portability to other ATMEGA MCUs, I2C and SPI EEPROM support (PRO)

**Features:** Vision Pro support

**In-app purchases (10)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlock PRO feature | $1.99 | one-time |
| SPI OLED | $1.99 | one-time |
| I2C OLED | $1.99 | one-time |
| Wifi home automation | $1.99 | one-time |
| 2.2" TFT | $1.99 | one-time |
| LoRa home automation | $1.99 | one-time |
| Home automation using Siri | $2.99 | one-time |
| Home automation using Google | $2.99 | one-time |
| BT home automation | $4.99 | one-time |
| BLE home automation | $4.99 | one-time |


## Frequently asked questions

### Is 555 Calc free?

555 Calc is free to download, with no in-app purchases.

### Is AVR Tutorial free?

AVR Tutorial is free to download, with in-app purchases available.

### Which has better reviews, 555 Calc or AVR Tutorial?

AVR Tutorial is rated higher. 555 Calc averages 4.0 out of 5 from 3 ratings, while AVR Tutorial averages 5.0 from 2 ratings.

### Do 555 Calc or AVR Tutorial have ads?

555 Calc shows ads; AVR Tutorial does not.

### Which is updated more often, 555 Calc or AVR Tutorial?

555 Calc ships an update every 20 months, and AVR Tutorial every 3 months. Most recently, 555 Calc was updated on September 27, 2026 and AVR Tutorial on September 24, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*