DuctChecker vs Bolt Length
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
DuctChecker
Easily calculate duct dimensions using various engineering methods like constant pressure, static pressure regain, total pressure, and velocity. This tool simplifies complex duct design calculations, typically found in flow diagrams or slide rules.
- Constant pressure method calculation
- Static pressure regain method
- Total pressure method
- Velocity method
- Duct dimension determination
- Simplified duct design
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To determine the size of the duct constant pressure method, static pressure regain method, total pressure method, velocity method. Generally uses constant pressure method. This constant pressure method is how to determine the duct dimensions using the same value per 1 m on all duct friction loss. Usually determined by flow diagrams or duct design for slide rules. You can easily determine the duct by using this program.
Bolt Length
This application helps calculate the length of metric coarse screws based on Japanese Industrial Standards. It is designed for mechanical design purposes and should be used at the user's own risk.
- Metric coarse screw length calculation
- Conforms to Japanese Industrial Standards (JIS)
- Designed for mechanical design
- User risk disclaimer
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This app is an application for calculating the length of the screw. ※:This app does not guarantee the effectiveness of the combination. ※:Use this application at your own risk. Conforms to the Japanese Industrial Standards (JIS). Screws are all metric coarse screw. For mechanical design. Sorry, Only in Japan.Because using the JIS.
Screenshots
Verdict
The clearest difference is price: Bolt Length at Free against DuctChecker's $6.99. Bolt Length also leads on review sentiment (33% vs 0%). DuctChecker's advantage is in-app purchases (none vs 1) and ads (none vs shown). On 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
Bolt Length is free to download; DuctChecker costs $6.99 up front. Bolt Length sells 1 one-off in-app purchase. DuctChecker asks for nothing beyond the download.
DuctChecker ships an update every 4 months, Bolt Length every 20 months. The most recent releases landed on September 7, 2026 and August 2, 2026 respectively.
| Parameter | DuctChecker | Bolt Length |
|---|---|---|
| Price | $6.99 | Free — better |
| Rating | — | 3.0 (2 ratings) — better |
| Positive reviews | 0.0% of reviews | 33.3% of reviews — better |
| Number of ratings | — | 2 — better |
| Update frequency | Every 4 months — better | Every 20 months |
| Ads | No — better | Yes |
| In-app purchases | No — better | Yes |
| Monetization | Paid | Free with in-app purchases — better |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 15.0 | 14.0 — better |
| Further details — not scored | ||
| Size | 23 MB | 6 MB |
| Age rating | 4+ | 4+ |
| Developer | AIR DESIGN, INC. | mitsunori oishi |
Customer experience
DuctChecker
Bolt Length
In-app purchases
DuctChecker
No in-app purchases
Bolt Length
- Hide Ads$1.99
