Quick answers to the questions every builder asks: where does it balance, how long will it fly, how will it handle, how much current can my pack give, and how hard will it pull. All instant, all free. For a full design, use the Airplane Designer.
Put in your wing chord and get the balance point — how far behind the leading edge the plane should sit level on your fingertips, with the battery in.
How long a pack lasts at your average current draw, landing with a 20% reserve (never run a LiPo flat).
Weight per wing area predicts how a plane handles and lands. Cubic wing loading (WCL) makes it comparable across sizes.
How many amps your pack can actually deliver — and whether it covers your setup's full-throttle draw.
Ballpark thrust from input watts and prop type, plus thrust-to-weight if you enter your plane's weight.
Most beginner crashes trace back to a number nobody checked. These quick calculators cover the ones that matter most on a scratch build — get them in range and the plane is forgiving; ignore them and no amount of stick skill saves it.
The single most important number. Measured as a percentage of the wing chord (the distance from the leading edge to the trailing edge), a safe starting CG for most trainers is around 25–33% back from the leading edge. Too far back (tail-heavy) makes a plane violently pitchy and usually un-flyable; slightly forward (nose-heavy) is safe and stable. Enter your chord and this gives you the exact spot to balance on two fingers.
Weight divided by wing area, usually in grams per square decimetre (g/dm²). It tells you how fast the plane has to move to stay in the air. Light wing loading (a park flyer around 30–50 g/dm²) means slow, floaty, beginner-friendly; high wing loading means fast and demanding. If your plane feels like it has to be thrown hard and flown fast, its wing loading is high.
The rest cover the power system: estimated flight time from battery capacity and average current, the maximum safe current your battery's C-rating allows, and static thrust versus weight (aim for at least a 1:2 thrust-to-weight ratio for a trainer, closer to 1:1 for something sporty).
Where should my CG be? Start at 25–33% of the chord and, if unsure, err slightly nose-heavy. What's a good wing loading for a first plane? Lower is easier — keep a trainer light. How do I use these numbers? Design the plane in the Airplane Designer, then use these to sanity-check it before you fly.
Numbers dialed in. Save a clean one-page spec sheet you can print for the field or share.
