Propeller Aircraft Range Calculator (Simplified Breguet)
Estimate cruise range from propulsive efficiency, specific fuel consumption, lift-to-drag ratio and gross/final weight — or invert the equation to find the L/D or final weight needed to hit a target range.
ηp ↑
Range scales directly with propulsive efficiency — a better-matched or constant-speed propeller converts more shaft power into usable thrust power.
cp ↓
Range scales inversely with specific fuel consumption — a thriftier engine stretches the same fuel load into more distance.
CL/CD ↑
Range scales directly with aerodynamic (lift-to-drag) efficiency — cleaner airframes and higher aspect-ratio wings fly farther on the same fuel.
Wi/Wf ↑
Range grows only with the logarithm of the weight ratio, so each extra unit of fuel adds progressively less range — diminishing returns.
How to Use This Calculator
The propeller range equation links five quantities: propulsive efficiency, specific fuel consumption, lift-to-drag ratio, gross weight, and final weight. Set the parameters you know, pick what to solve for, and read the result.
1. Pick a unit system
Choose Imperial (lb, hp) or Metric (kg, kW). The calculator swaps in the correct built-in conversion constant and typical defaults for that system.
2. Set propulsive efficiency
Use a preset pill (fixed-pitch, constant-speed, optimal) or drag the slider to enter a custom η_p.
3. Set specific fuel consumption
Choose a piston or turboprop preset for c_p, or type a value from your engine's data sheet.
4. Choose what to solve for
Pick "Range" if you know L/D and both weights, or "C_L/C_D" / "W_f" if you have a target range and want to find the aerodynamic efficiency or final weight needed to reach it.
5. Enter the known values
Fill in whichever fields remain editable — the greyed-out field with the "SOLVED" tag is the one being computed.
6. Switch to Advanced
See how ±1% changes in each input move the result, plus fuel burned, fuel fraction, and the overall range factor.
What This Tool Offers
Built around the simplified propeller Breguet range equation used for early-stage cruise performance estimates on piston and turboprop aircraft.
Solve any direction
Find the range from known aircraft data, or work backward from a target range to the required L/D or final weight.
Dual unit systems
Switch between Imperial (lb, hp) and Metric (kg, kW) — each with the correct dimensional constant (375, 326, or 367) applied automatically.
Realistic presets
Quick presets for propeller efficiency and specific fuel consumption covering fixed-pitch, constant-speed, piston, and turboprop configurations.
Transparent step-by-step math
Every calculation shows the intermediate log term and substitution — not just the final number — so results can be checked by hand.
Built-in sensitivity check
See how much the result moves for a ±1% nudge in any input, useful for quick design-margin and tolerance checks.
Companion performance metrics
Advanced mode also reports fuel burned, fuel weight fraction, and the aircraft's overall range factor.
What Is the Breguet Range Equation for Propeller Aircraft?
The propeller (Breguet) range equation estimates how far an aircraft can fly on its fuel load during cruise, assuming steady, level flight at a roughly constant lift-to-drag ratio. It separates the problem into a propulsion term (how efficiently power becomes thrust, and how much fuel that power costs) and an aerodynamic term (how much lift a given amount of drag buys), multiplied by the natural log of how much the aircraft's weight drops as fuel burns off.
Formula and Variables
| Symbol | Meaning | Typical range |
|---|---|---|
| η_p | Propulsive (propeller) efficiency | 0.7 – 0.9 |
| c_p | Specific fuel consumption per unit shaft power | 0.4 – 0.6 lb/(hp·hr); 0.24 – 0.37 kg/(kW·hr) |
| C_L/C_D | Cruise lift-to-drag ratio | 8 – 18 for typical propeller aircraft |
| W_i, W_f | Initial (gross) and final aircraft weight | W_f < W_i, difference is fuel burned |
| K | Unit-consistency constant (applied automatically) | 375 (mi), 326 (nmi), 367 (km) |
Because cp is conventionally quoted per horsepower-hour or kilowatt-hour rather than in pure length units, a constant K is needed to make the equation dimensionally correct in the distance unit you want — this calculator applies it automatically based on the units you select.
Worked Example
ln(6600/5290) = ln(1.2477) = 0.2212
R = 375 × (0.85/0.45) × 12 × 0.2212
R = 375 × 1.889 × 12 × 0.2212 ≈ 1,880 mi
Frequently Asked Questions
As fuel burns off, the aircraft gets lighter, needs less lift, and therefore less thrust and fuel flow for the same speed. Integrating that continuously changing fuel flow over the flight produces a natural logarithm of the weight ratio, not a linear term.
The jet form uses thrust-specific fuel consumption and includes cruise velocity explicitly, since jet engines are rated by thrust rather than shaft power. The propeller form instead uses power-specific fuel consumption together with a separate propulsive efficiency term, since velocity cancels out of the power-based derivation.
Speed appears in both the thrust-power-available term and the time-to-cover-distance term, and the two cancel exactly when the equation is derived, leaving range dependent only on efficiency, fuel consumption, aerodynamic efficiency, and weight ratio.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| R | Range | m |
| η_p | Propeller efficiency | |
| c_p | Specific fuel consumption (power-based) | 1/s |
| C_L/C_D | Lift-to-drag ratio | |
| W_i | Initial weight | N |
| W_f | Final weight | N |
What it means
The Breguet range equation for propeller aircraft is similar to that for jets but uses power‑specific fuel consumption (c_p) and propeller efficiency. Range is maximised by flying at the speed for maximum L/D. This equation is used in conceptual design to estimate range for a given fuel fraction. Understanding this relation is essential for aircraft sizing and for performance analysis of propeller‑driven aircraft.
Worked example
Propeller Aircraft Range – Two Examples
Real‑World| Parameter | Value |
|---|---|
| η_p | 0.8 |
| c_p | 8×10⁻⁸ |
| L/D | 15 |
| Wᵢ/W_f | 15000/11000 = 1.364 |
| Parameter | Value |
|---|---|
| η_p | 0.82 |
| c_p | 7.5×10⁻⁸ |
| L/D | 16 |
| ln(20000/14500) | 0.321 |
Common mistakes
- Propeller aircraft range (simplified): R = (η_p / c_p) · (C_L/C_D) · ln(W_i/W_f).
- η_p: Propeller efficiency.
- c_p: Specific fuel consumption (kg/(W·s) or similar).
- Assumes constant L/D and c_p.
- Maximum range occurs at (C_L/C_D) max.
Applications
Propeller aircraft range (simplified) gives the cruise range for a propeller‑driven aircraft. It is similar to the Breguet range but uses propulsive efficiency and brake specific fuel consumption. Engineers use this to size fuel tanks, to compare aircraft designs, and to optimise cruise speed. By maximising range, aerospace engineers can meet mission requirements with lower fuel consumption, improving operational efficiency and cost.
- Preliminary design of light aircraft, turboprops, and UAVs
- Range‑payload trade‑off studies
- Optimisation of cruise speed and altitude
- Engine and propeller selection for long‑range missions
- Performance benchmarking of propeller aircraft
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