# uSpectrum PAR vs VPD Chart

The clearest difference is rating: VPD Chart at 4.5 against uSpectrum PAR's 1.0. VPD Chart also leads on update cadence (every 3 weeks vs every 8 months) and ratings volume (30 vs 2). uSpectrum PAR's advantage is in-app purchases (none vs 2) and iOS requirement (9.0 vs 15.1). On price, ads and device support there is nothing between them.

Both are free to download. VPD Chart sells 2 in-app purchases, starting at $3.99 per month. uSpectrum PAR asks for nothing beyond the download.

VPD Chart holds the better App Store score, 4.5 against 1.0. That said, the two scores are not equally well evidenced: VPD Chart has 30 ratings behind it against 2, so its average is the more settled of the two.

uSpectrum PAR ships an update every 8 months, VPD Chart every 3 weeks. The most recent releases landed on September 16, 2026 and October 9, 2026 respectively.

## The numbers

| Metric | uSpectrum PAR | VPD Chart |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [1.0 (2 ratings)](https://appshunter.io/ios/app/uspectrum-par/id1466017397/reviews) | **[4.5 (30 ratings)](https://appshunter.io/ios/app/vpd-chart/id6470015847/reviews)** |
| Number of ratings | 2 | **30** |
| Positive reviews | — | 73.7% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 8 months | **Every 3 weeks** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 25 MB | 49 MB |
| Requires iOS | **9.0** | 15.1 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [United Power Research Technology Corporation](https://appshunter.io/developer/1501316337) | [INNOVO DEV S.R.L.](https://appshunter.io/developer/1814828527) |

## What reviewers say

### uSpectrum PAR

[App page](https://appshunter.io/ios/app/uspectrum-par/id1466017397)

This application connects wirelessly to a handheld spectral PAR meter, allowing remote analysis and configuration of light sources. It displays detailed spectral data, light source information, and absorption metrics, with options to save and share measurements.

**Highlights:** Wireless Bluetooth connection, Remote light source analysis, Save captured data, Display spectrum and CIE diagrams, View light source metrics (LUX, CCT, CRI), Share measured data via email

**Features:** macOS Compatibility

**In-app purchases:** none


### VPD Chart

[App page](https://appshunter.io/ios/app/vpd-chart/id6470015847)

This app calculates Vapor Pressure Deficit (VPD) using air temperature, relative humidity, and canopy temperature. It offers real-time charting, sensor integration, and educational tools to understand plant growth environments. Organize data by zones and visualize dew point areas.

**Highlights:** VPD calculation, Interactive VPD chart, Sensor integration, Zone organization, Dew point visualization, Grow Timeline

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| VPD Chart Plus (monthly) | $3.99 | per month |
| VPD Chart Plus (annual) | $29.99 | per year |


## Frequently asked questions

### Is uSpectrum PAR free?

uSpectrum PAR is free to download, with no in-app purchases.

### Is VPD Chart free?

VPD Chart is free to download, with in-app purchases available.

### Which has better reviews, uSpectrum PAR or VPD Chart?

VPD Chart is rated higher. uSpectrum PAR averages 1.0 out of 5 from 2 ratings, while VPD Chart averages 4.5 from 30 ratings.

### Do uSpectrum PAR or VPD Chart have ads?

Neither uSpectrum PAR nor VPD Chart shows ads.

### Which is updated more often, uSpectrum PAR or VPD Chart?

uSpectrum PAR ships an update every 8 months, and VPD Chart every 3 weeks. Most recently, uSpectrum PAR was updated on September 16, 2026 and VPD Chart on October 9, 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.*