# Timer 555 Calculator Pro vs Electronics Reference Toolkit

The clearest difference is price: Electronics Reference Toolkit at Free against Timer 555 Calculator Pro's $0.99. Electronics Reference Toolkit also leads on update cadence (fortnightly vs every 3 months) and rating (4.9 vs 4.7). Timer 555 Calculator Pro's advantage is device support (3 vs 1) and iOS requirement (13.2 vs 16.6). On ratings volume, ads and in-app purchases there is nothing between them.

Electronics Reference Toolkit is free to download; Timer 555 Calculator Pro costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Electronics Reference Toolkit holds the better App Store score, 4.9 against 4.7. Both are backed by a comparable volume of ratings — 3 and 7 respectively.

Timer 555 Calculator Pro ships an update every 3 months, Electronics Reference Toolkit fortnightly. The most recent releases landed on October 5, 2026 and October 6, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator Pro | Electronics Reference Toolkit |
| --- | --- | --- |
| Price | $0.99 | **Free** |
| Rating | [4.7 (3 ratings)](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125/reviews) | **[4.9 (7 ratings)](https://appshunter.io/ios/app/electronics-reference-toolkit/id6757098692/reviews)** |
| Number of ratings | 3 | **7** |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 3 months | **Fortnightly** |
| Monetization | Paid | **Free** |
| Size | 3 MB | 7 MB |
| Requires iOS | **13.2** | 16.6 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [Ha Do Thi Thu](https://appshunter.io/developer/1707030622) |

## What reviewers say

### Timer 555 Calculator Pro

[App page](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125)

Calculate parameters for monostable and astable circuits. Find component combinations for desired pulse width or frequency. Share circuit files via iCloud Drive or AirDrop.

**Highlights:** Calculate monostable pulse width, Calculate astable frequency, Find component combinations, Adjust component tolerance, Unlimited combinations (Pro), Share circuit files

**In-app purchases:** none


### Electronics Reference Toolkit

[App page](https://appshunter.io/ios/app/electronics-reference-toolkit/id6757098692)

This app provides a comprehensive suite of tools for electronics calculations and reference. It includes calculators for resistors, LEDs, capacitors, and voltage dividers, along with a unit converter and transistor database. Designed for speed and offline use, it's ideal for students, hobbyists, and engineers.

**Highlights:** Resistor Calculator (4/5 band), Ohm's Law Calculator, LED Resistor Calculator, Capacitor Decoder, Voltage Divider Calculator, Unit Converter, Transistor Reference

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Timer 555 Calculator Pro free?

Timer 555 Calculator Pro costs $0.99, with no in-app purchases.

### Is Electronics Reference Toolkit free?

Electronics Reference Toolkit is free to download, with no in-app purchases.

### Which has better reviews, Timer 555 Calculator Pro or Electronics Reference Toolkit?

Electronics Reference Toolkit is rated higher. Timer 555 Calculator Pro averages 4.7 out of 5 from 3 ratings, while Electronics Reference Toolkit averages 4.9 from 7 ratings.

### Do Timer 555 Calculator Pro or Electronics Reference Toolkit have ads?

Neither Timer 555 Calculator Pro nor Electronics Reference Toolkit shows ads.

### Which is updated more often, Timer 555 Calculator Pro or Electronics Reference Toolkit?

Timer 555 Calculator Pro ships an update every 3 months, and Electronics Reference Toolkit fortnightly. Most recently, Timer 555 Calculator Pro was updated on October 5, 2026 and Electronics Reference Toolkit on October 6, 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.*