SAC Rate Scuba
SAC Rate Scuba is a local-first manual reference calculator for scuba gas math. Version 1.0 has three modes: SAC, Gas Needed, and Runtime.
What does the app calculate?
The app can:
- estimate SAC pressure rate and surface RMV from start pressure, end pressure, average depth, dive time, and a selected cylinder
- backsolve gas needed and minimum start pressure from surface RMV, planned depth, planned time, and reserve pressure
- estimate cylinder runtime from surface RMV, planned depth, start pressure, and reserve pressure
Which inputs does the app use?
Version 1.0 is manual entry only. Depending on the mode, you enter:
- measurement system:
imperialormetric - water type:
saltorfresh - cylinder capacity or water volume
- cylinder rated pressure
- dive start pressure and end pressure
- average or planned depth
- dive or planned time
- surface RMV
- reserve pressure
- start pressure for runtime estimates
What formulas does the app use?
The formulas are shown transparently in the app. The core relationships are:
- ambient pressure ATA =
1 + depth / water divisor - gas rate at depth = surface RMV x ambient pressure
- gas needed = gas rate at depth x planned time
- minimum start pressure = required pressure + reserve pressure
- runtime = usable gas / gas rate at depth
- SAC analysis uses pressure drop, dive time, ambient pressure, and the selected cylinder factor to estimate SAC pressure rate and surface RMV
The app follows standard SAC and RMV estimation math of the kind described in DAN's [Estimating Your Air Consumption](https://dan.org/alert-diver/article/estimating-your-air-consumption/).
Does the app replace a dive computer?
No. SAC Rate Scuba is manual reference only. It does not replace a dive computer, formal dive planning process, team procedures, or in-water judgment.
Does the app calculate decompression or no-decompression limits?
No. Version 1.0 does not do decompression planning, no-decompression limits, gas-switch planning, or ascent scheduling.
Does the app log dives, use GPS, or connect to a tank transmitter?
No. Version 1.0 does not do GPS, maps, dive logging, Bluetooth pairing, dive computer sync, or live tank integration.
Does the app work offline?
Yes. The app is local-first and does not require a network connection for core calculations.
Why is the app framed as manual reference only?
Because that is the actual product scope. The app stays deliberately narrow so the math, the feature list, and the App Store metadata all match. Apple's App Review guidance for apps with physical-risk implications pushes toward exact metadata and away from live safety or emergency claims, so SAC Rate Scuba keeps everything manual and transparent.
Are the results guaranteed or suitable for emergencies?
No. Use the app as a reference starting point only. Always confirm your gas plan and dive decisions with your own training, dive computer, tables, team procedures, and current conditions. Do not use the app as emergency decision support.
Are my values synced anywhere?
No. Version 1.0 has no account system and no cloud sync.
Contact
- Support email:
yangguangwin@icloud.com - Include your device model, iOS version, app version, measurement system, and reproduction steps when you report an issue.