# Privacy Policy - Duct Calc Pro

**Last Updated: July 20, 2026**

## Overview

Duct Calc Pro (ダクト計算 Pro) is an HVAC duct-sizing calculator for air-conditioning and ventilation engineers, developed by WittyApps. All calculations run entirely on your device. We collect a minimal amount of anonymous data to keep the app reliable, described below.

## Information We Collect

- **Anonymous usage analytics** (via Amplitude): which calculators are opened and whether the Pro unlock screen is shown or purchased. No names, emails, or account identifiers exist in the app, so none are collected.
- **Crash reports** (via Sentry): if the app crashes, technical details (device model, OS version, stack trace) are sent so we can fix the bug.

We do NOT collect your dimensions, airflow values, inputs, location, contacts, photos, or any personally identifying information. There are no accounts and no advertising.

## How We Use Information

Usage analytics tell us which calculators matter so we can improve them. Crash reports tell us when something breaks so we can fix it. Nothing is used for advertising, profiling, or cross-app tracking, and data is never sold.

## Data Storage

Your last-used settings and Pro purchase state are stored only on your device. Deleting the app removes them. Analytics and crash data are stored by our service providers (Amplitude, Sentry) under their own security policies.

## Third-Party Services

- **Amplitude** (anonymous product analytics) — see Amplitude's privacy policy.
- **Sentry** (crash reporting) — see Sentry's privacy policy.
- **Apple App Store / Google Play** (in-app purchases) — payment is processed entirely by Apple or Google; we never see your payment information.

## Your Rights

Analytics data is anonymous and cannot be tied back to you, which means there is no personal profile for us to access, correct, or export. If you have any concern, contact us and we will help.

## Data Security

Your dimensions and inputs never leave your device. Analytics and crash data are transmitted over encrypted connections (HTTPS).

## Children's Privacy

The app is a professional trade tool and collects no personal data from anyone, including children under 13.

## Changes to This Policy

If this policy changes, the updated version will be posted on this page with a new "Last Updated" date.

## Data Retention

Your data in the app (entries, calculations, and settings) is stored solely on your device. It is never transmitted to or stored on our servers. This data is retained on your device until you delete it or uninstall the app, at which point it is permanently and irreversibly removed. We keep no backups of your personal data on any server.

The anonymous usage analytics and crash reports described above are retained by our service providers (Amplitude, Sentry) in accordance with their data-retention policies and contain no personal identifiers we could use to identify you.

Advertising-related data processed by Google AdMob is retained in accordance with Google's privacy policy; we do not receive or store it ourselves.

## Contact Us

If you have questions about this policy, contact: [email protected]