# Max Zs Values vs The Voltage Drop Calc

The clearest difference is price: The Voltage Drop Calc at Free against Max Zs Values's $9.99. Max Zs Values's advantage is in-app purchases (none vs 3) and iOS requirement (11.0 vs 17.6). On update cadence, ads and device support there is nothing between them.

The Voltage Drop Calc is free to download; Max Zs Values costs $9.99 up front. The Voltage Drop Calc sells 3 in-app purchases, starting at $4.99 per month. Max Zs Values asks for nothing beyond the download.

Max Zs Values ships an update every 4 months, The Voltage Drop Calc every 3 months. The most recent releases landed on November 6, 2026 and October 30, 2026 respectively.

## The numbers

| Metric | Max Zs Values | The Voltage Drop Calc |
| --- | --- | --- |
| Price | $9.99 | **Free** |
| Positive reviews | 55.2% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 4 months | **Every 3 months** |
| Monetization | Paid | — |
| Size | 15 MB | 7 MB |
| Requires iOS | **11.0** | 17.6 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Pro Certs Software Ltd](https://appshunter.io/developer/444429696) | [1BIGRIG Ltd](https://appshunter.io/developer/1792073283) |

## What reviewers say

### Max Zs Values

[App page](https://appshunter.io/ios/app/max-zs-values/id498838137)

This app calculates and displays maximum permitted Zs values for electrical installations, adhering to the 18th Edition of BS 7671. It includes 80% temperature adjusted values and manufacturer charts for MCCB devices, along with a converter for older Zs values.

**Highlights:** 100% BS 7671 Zs Values, 80% On Site Guide Zs Values, Adjustable disconnection times (0.4s, 0.2s, 5s), BS EN Device Zs calculation, MCCB 60947-2 Zs charts, Zs Converter for 18th edition

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### The Voltage Drop Calc

[App page](https://appshunter.io/ios/app/the-voltage-drop-calc/id6756492539)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| GoPro Monthly | $4.99 | per month |
| GoPro Yearly | $24.99 | per year |
| Remove Ads | $24.99 | one-time |


## Frequently asked questions

### Is Max Zs Values free?

Max Zs Values costs $9.99, with no in-app purchases.

### Is The Voltage Drop Calc free?

The Voltage Drop Calc is free to download, with in-app purchases available.

### Do Max Zs Values or The Voltage Drop Calc have ads?

Neither Max Zs Values nor The Voltage Drop Calc shows ads.

### Which is updated more often, Max Zs Values or The Voltage Drop Calc?

Max Zs Values ships an update every 4 months, and The Voltage Drop Calc every 3 months. Most recently, Max Zs Values was updated on November 6, 2026 and The Voltage Drop Calc on October 30, 2026.

---

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