Weight Effect on Takeoff Distance Calculator
The W² law in action: see how each passenger, bag and gallon stretches the takeoff roll — and what off-loading buys back.
Weight hits twice: liftoff speed rises with √W (squared in the kinetic energy) and acceleration falls as 1/W at fixed thrust. The same law explains why 8% over gross — 'just a little heavy' — adds 16%+ of runway you may not have.
Formula
⚠️ Planning estimate only — your POH/AFM performance charts are the authoritative source. Always verify with official data, and apply your operator's safety factors. Not for airworthiness decisions.
The W² law in action: see how each passenger, bag and gallon stretches the takeoff roll — and what off-loading buys back.
About Weight Effect on Takeoff Distance Calculator
Of all the levers on takeoff performance — altitude, temperature, wind, surface — weight is the only one the pilot fully controls at the hold-short line. This calculator demonstrates the weight-squared law: distance scales with (W₂/W₁)², so modest-sounding load changes move the roll dramatically. It also prices each marginal 100 lb in feet of runway, which turns 'should we top the tanks?' into arithmetic.
How to use Weight Effect on Takeoff Distance Calculator
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula distance₂ = distance₁ × (W₂/W₁)² substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Weight Effect on Takeoff Distance Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula distance₂ = distance₁ × (W₂/W₁)² with sources cited on the page
- ✓Weight hits twice: liftoff speed rises with √W (squared in the kinetic energy) and acceleration falls as 1/W at fixed thrust. The same law explains why 8% over gross — 'just a little heavy' — adds 16%+ of runway you may not have.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why weight squared and not just proportional?+
Two compounding effects. Lift-off speed must rise with the square root of weight (lift ∝ V²), and kinetic energy at that speed therefore rises linearly with weight — but the engine also accelerates a heavier mass more slowly (a ∝ T/W). Energy needed up, rate of gaining it down: the product is the square law.
How much runway does flying 200 lb under gross actually save?+
At a 2,550 lb reference with a 1,300 ft roll, departing at 2,350 lb cuts the roll about 15% — nearly 200 ft — and improves the climb gradient on top. On a marginal strip, leaving one fuel stop's worth of gas (and planning a stop) is frequently the difference between comfortable and ugly.
Does the square law hold for the obstacle-clearance distance too?+
Approximately, and slightly worse: the air segment depends on climb rate, which degrades a touch faster than W² because excess power shrinks at both ends (more power required, same power available). POH charts capture the full effect — which is why their weight columns diverge faster for the 50-ft figure than for ground roll.
What about flying over maximum gross weight?+
Beyond the legality and the insurance vacuum, you're off the chart in the literal sense — no published data exists, stall speeds rise, climb gradient sags, and structural margins (designed to gross, factored for certification) erode. The calculator will happily extrapolate the math for education; the aircraft's certificate will not.
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