Download CG Calc apk Varies with device free for Android smartphone

19 Jul
CG Calc

Posted by Graham Dyer in Tools | July 19, 2016 | 6 Comments

Apk file size: 1.3 MB

RC Model Aircraft Center of Gravity Calculator v3 (replaces v1.x and v2.x)

This app is COMPLETELY free, no ads and no in-app purchases.

Note 1: Please see my RC-E Calculator which includes wing loading, flight time, prop thrust, energy density, current draw and many other calculators:
Google Play Store Link ► RC E Calc Pro
Note 2: Please email if you have a problem or suggestion
Note 3: This app was built with MIT App Inventor, the permissions* (see below) required are the defaults, I have no control over what permissions Google/MIT App Inventor requires an app to have. This app has been published on Google Play for 4 years since 2012 and since it is still here you can be assured that Google Play has no problems with it.


This may prevent your plane from crashing!

"A nose-heavy airplane may not fly well, but a tail-heavy airplane may fly only once."

This app will calculate the POSITION of the Center of Gravity (CG or CoG or Balance Point) measured back from the leading edge at the wing root in the units of your choice.

Enter your measurements for:
- tip chord length,
- root chord length,
- sweep length and
- required CG percentage (eg 28%)

of your model airplane and then the CG, wing area, geometric mean chord and tip-to-root chord ratio will be calculated automatically.

You can use inches or centimeters and the result will be in the units you used (don't mix units though).

A too rearward CG position can cause unrecoverable (potentially fatal) instability!

25-35% recommended for most conventional wings, 12-18% for pure flying wings, 15-19% for Delta wings.

This calculator uses the Neutral Point, the AIRCRAFT'S aerodynamic center (AC), as a reference point to calculate the CG range. It uses a well known, simple but fairly reliable method of determining the CG of a model aircraft.

Thanks for downloading, comments and ratings welcome.

Version history:

- improved layout
- new image
- improved wording

- improved layout
- improved images
- new instruction page
- corrected wording

Version 2.2:
- Resize & refit for tablets
- Refit text flow for large numbers
- Center everything
- Minor layout improvement & bug fixes

Version 2.0+: implemented due to Google licensing changes.
- No longer requires a button tap to calculate, calculates automatically after the all the fields are filled.
- Added wing Area calculation
- Changed layout for ease of use/visibility
- Fixed small bugs

(*This app requires the following default MIT App Inventor permissions:

android.permission.INTERNET - to check for updates and so that the screen's background image property can be set to the URL of an image on the web if there is a background image
android.permission.WRITE_EXTERNAL_STORAGE - to move the app to EXT SD on your phone if necessary.
android.permission.READ_PHONE_STATE - to check for incoming phone calls and then hide the app if necessary.
android.permission.READ_EXTERNAL_STORAGE - access the app on EXT SD if necessary.)

Whats new

    Version 3.01
    - improved layout
    - new image
    - improved wording

Graham Dyer part of our Tools and have average installs from 5000 to 10000. Last Update July 19, 2016. Google play rating is 86.2687. Current verison is Varies with device. Actual size 1.3 MB.

Download cg-calc.apk 1.3 MB


Tom Sawyer

Awesome Building my first rc plane from scratch, this is a big help, will update after maiden flight.

scott harland

Great!! A must have for anyone wanting to scratch build RC planes ! ;)

Roman Pronchenko

Must have for making a RC plane

Robert Emmons

For a free app...... This app works as good as the more complicated apps. Plus it's more user friendly for a scratch builder like me who doesn't need anything more than this.

Rizal Alfian

Good tools

Ken Nelson

Incomplete Should include tail volume and moment

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