RC plane CG calculator
Any layout, up to 5 wing panels, canards and V-tails. Get the balance point, neutral point and static margin, a 3-view drawing of your plane, and where to put the battery. Works for foam, balsa, fabric, fiberglass, carbon or printed airframes.
First flight: if your plans or kit show a CG further forward than this, use the more forward one. Move it back later in 3–5 mm steps.
Where does the battery go?
List your parts with their weight and position. Position is measured from the wing leading edge at the root: minus means in front of it. The helper finds your real CG and tells you how far to move the battery.
| Part | Weight | Position | Battery |
|---|
How to use it
- Pick your layout. An example plane loads so you can see how it works.
- Enter the root chord, then one row per wing panel: span, tip chord, sweep and dihedral. Add panels for elliptical, cranked or polyhedral wings.
- Do the same for the tail. For a V-tail, enter the panel length along the panel and the V angle. For a canard, the distance is negative.
- Balance the plane at the CG shown. With your fingers under the wing next to the fuselage, use the "measure at fuselage side" number: on a swept wing the leading edge there is further back than at the centre line.
- Use the weight & balance helper to find the battery position.
- Check side-to-side balance too: hold the plane by the spinner and the tail. If one wing drops, add a little weight to the other wing tip.
- For a VTOL quadplane, enter the front and rear lift motor positions. The CG must also sit near the middle of them for a steady hover.
Tail effectiveness
A tail sitting in the wing's wake or behind a fat fuselage works less well than one in clean air. Auto uses 0.85 for most tails, 0.95 for a T-tail and 1.0 for a canard. These lean to the safe side. Pick a lower value for a short tail close to the wing.
MAC, neutral point and static margin
The mean aerodynamic chord (MAC) is the average chord of the whole wing, including every panel. The neutral point is where the CG would make the plane neutrally stable. The static margin is the gap between the CG and the neutral point, as a percentage of the MAC: 10–20 % suits a plane with a tail, 5–10 % a flying wing or delta.
Typical values
| Plane type | CG (% MAC) | Tail volume |
|---|---|---|
| Trainer, high wing | 25–30 % | 0.5–0.7 |
| Sport / FPV cruiser | 25–33 % | 0.4–0.6 |
| Glider, V-tail glider | 30–38 % | 0.35–0.6 |
| 3D aerobatic | 30–35 % | 0.3–0.5 |
| Flying wing (swept) | 15–20 % | none |
| Delta | 15–22 % | none |
| Canard | ahead of the wing LE | negative |
Starting points. The static-margin check uses your real sizes. Always confirm the CG in flight, moving back in small steps.
Questions
Where should the CG be on an RC plane?
On a plane with a tail, usually 25–33 % of the mean aerodynamic chord (MAC) back from the leading edge. Flying wings and deltas need 15–20 %. This calculator finds your exact point from your own sizes.
What is the mean aerodynamic chord (MAC)?
The average chord of the whole wing, including taper, sweep and every panel. CG positions are given as a percentage of it.
What is static margin?
The gap between the CG and the neutral point, as a percentage of the MAC. 10–20 % suits a plane with a tail; 5–10 % suits a flying wing or delta.
Where do I measure the CG from?
From the wing leading edge at the centre line. The calculator also gives the distance from the leading edge next to the fuselage, where you put your fingers to balance.
How accurate is it?
The wing and tail geometry are exact. The neutral point uses standard textbook methods and leans to the safe side. Always confirm the CG in flight and move it back only in small steps.
Does it work for foam, balsa and composite planes?
Yes. The CG depends on shape and weights, not on material. It works for foam, balsa, fabric, fiberglass, carbon and 3D-printed planes.
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