Resistor Tools vs 555 Calc
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Resistor Tools
This utility app provides a suite of tools for calculating and determining resistor values. It assists hobbyists and engineers with series, parallel, and voltage divider calculations, as well as inverting amplifier gain.
- Series and parallel resistor calculation
- Resistor combination finder
- Voltage divider ratio and value calculation
- Inverting amplifier gain calculation
- Save combinations to CSV
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This app is a collection of resistor calculators. It is suitable for hobbyist or electronic engineer. * Calculate resistance of two resistors in series or parallel * Find out combinations of two resistors in series/parallel making a desired resistance * Calculate ratio of R1/R2 and voltage divider * Find out resistor values of making voltage divider ratio * Find out resistor values of making inverting amplifier gain * Save combination values in CSV file
555 Calc
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.
- Calculate resistor values
- Input frequency
- Input duty ratio
- Input capacitor value
- Timer IC 555 circuit design
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This App calculates registors value, when designing the circuit using Timer IC 555. How to (1) Input Frequency value. (2) Input Duty Ratio. (3) Input C1 Value. (4) Touch ‘Calculate’ button. (5) Registors value will be displayed. Note. * Set Duty Ratio to 50 ~ 99. * If you set Duty Ratio to 50, R1 value will be set to 0.
Screenshots
Verdict
The clearest difference is rating: Resistor Tools at 5.0 against 555 Calc's 4.0. Resistor Tools also leads on ads (none vs shown) and update cadence (every 2 months vs every 20 months). 555 Calc's advantage is in-app purchases (none vs 1). On price, device support and iOS requirement there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Resistor Tools sells 1 one-off in-app purchase. 555 Calc asks for nothing beyond the download.
Resistor Tools holds the better App Store score, 5.0 against 4.0. Both are backed by a comparable volume of ratings — 10 and 3 respectively. Written reviews point the same way: 75% of Resistor Tools's written reviews are positive against 50% of 555 Calc's.
Resistor Tools ships an update every 2 months, 555 Calc every 20 months. The most recent releases landed on October 10, 2026 and September 27, 2026 respectively.
| Parameter | Resistor Tools | 555 Calc |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (10 ratings) — better | 4.0 (3 ratings) |
| Positive reviews | 75.0% of reviews — better | 50.0% of reviews |
| Number of ratings | 10 — better | 3 |
| Update frequency | Every 2 months — better | Every 20 months |
| Ads | No — better | Yes |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | Ad-supported — better |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 12.0 | 11.0 — better |
| Further details — not scored | ||
| Size | 4 MB | 18 MB |
| Age rating | 4+ | 4+ |
| Developer | Siu Yuen Ho | Jibiki Works |
Customer experience
Resistor Tools
555 Calc
In-app purchases
Resistor Tools
- Unlock pro feature$0.99
555 Calc
No in-app purchases
Questions
Is Resistor Tools free?
Is 555 Calc free?
Which has better reviews, Resistor Tools or 555 Calc?
Do Resistor Tools or 555 Calc have ads?
Which is updated more often, Resistor Tools or 555 Calc?
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