# Timer 555 Calculator Pro vs 555 Calc

The clearest difference is review sentiment: Timer 555 Calculator Pro at 100% against 555 Calc's 50%. Timer 555 Calculator Pro also leads on rating (4.7 vs 4.0) and ads (none vs shown). 555 Calc's advantage is price (Free vs $0.99) and iOS requirement (11.0 vs 13.2). On ratings volume, in-app purchases and device support there is nothing between them.

555 Calc 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.

Timer 555 Calculator Pro holds the better App Store score, 4.7 against 4.0. Both are backed by a comparable volume of ratings — 3 and 3 respectively. Written reviews point the same way: 100% of Timer 555 Calculator Pro's written reviews are positive against 50% of 555 Calc's.

Timer 555 Calculator Pro ships an update every 3 months, 555 Calc every 20 months. The most recent releases landed on October 23, 2026 and October 13, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator Pro | 555 Calc |
| --- | --- | --- |
| Price | $0.99 | **Free** |
| Rating | **[4.7 (3 ratings)](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125/reviews)** | [4.0 (3 ratings)](https://appshunter.io/ios/app/555-calc/id868058244/reviews) |
| Number of ratings | 3 | 3 |
| Positive reviews | **100.0% of reviews** | 50.0% of reviews |
| In-app purchases | No | No |
| Ads | **No** | Yes |
| Update frequency | **Every 3 months** | Every 20 months |
| Monetization | Paid | **Ad-supported** |
| Size | 3 MB | 18 MB |
| Requires iOS | 13.2 | **11.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [Jibiki Works](https://appshunter.io/developer/556845808) |

## 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


### 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


## Frequently asked questions

### Is Timer 555 Calculator Pro free?

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

### Is 555 Calc free?

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

### Which has better reviews, Timer 555 Calculator Pro or 555 Calc?

Timer 555 Calculator Pro is rated higher. Timer 555 Calculator Pro averages 4.7 out of 5 from 3 ratings, while 555 Calc averages 4.0 from 3 ratings.

### Do Timer 555 Calculator Pro or 555 Calc have ads?

555 Calc shows ads; Timer 555 Calculator Pro does not.

### Which is updated more often, Timer 555 Calculator Pro or 555 Calc?

Timer 555 Calculator Pro ships an update every 3 months, and 555 Calc every 20 months. Most recently, Timer 555 Calculator Pro was updated on October 23, 2026 and 555 Calc on October 13, 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.*