Thrust Specific Fuel Consumption (TSFC)

Fuel mass flow rate consumed per unit of thrust produced, a key measure of jet engine fuel efficiency.

Written by the Vorzep Team

PropulsionAircraft PerformanceEfficiency

TSFCṁ_fT

Solve for:

TSFC ṁ_f T

Engine Presets

Select engine: Set values

Units

System:

Enter the other two values

kg/(N·h)

kg/h

TSFC = fuel consumed per unit thrust per hour Lower TSFC = better fuel efficiency Typical TSFC: 0.4–0.9 lb/(lbf·h) for jet engines

Variables

Symbol	Quantity	Unit
TSFC	Thrust specific fuel consumption	kg/(N*s)
mdot_f	Fuel mass flow rate	kg/s
T	Thrust	N

What it means

TSFC is a key engine performance parameter, indicating how much fuel is consumed per unit thrust. It is typically expressed in kg/(N·s) or lb/(lbf·h). Lower TSFC means better fuel economy. TSFC varies with altitude, speed, and throttle setting. It is used in the Breguet range equation and in mission analysis. Understanding TSFC is essential for comparing engines and for evaluating propulsion system efficiency.

Worked example

TSFC – Two Examples

Real‑World

Scenario: Fuel flow ṁ_f = 0.36 kg/s, thrust T = 20,000 N. Find TSFC.

Parameter	Value
ṁ_f	0.36 kg/s
T	20,000 N

1TSFC = ṁ_f/T = 0.36/20000 = 1.8×10⁻⁵ kg/(N·s)

Result 1.8×10⁻⁵ ✓ Efficient

Scenario: ṁ_f = 0.5, T = 25,000. Find TSFC.

Parameter	Value
ṁ_f	0.5
T	25,000

1TSFC = 0.5/25000 = 2.0×10⁻⁵ kg/(N·s)

Result 2.0×10⁻⁵ ✓ Typical

Key insight: TSFC is fuel consumption per unit thrust – lower is more efficient.

Common mistakes

Thrust specific fuel consumption: TSFC = ṁ_f / T.
Units: kg/(N·s) or 1/s (since N = kg·m/s², so kg/(N·s) = kg/(kg·m/s²·s) = s/m? Actually, TSFC is typically given in kg/(N·h) or lb/(lbf·h). In SI, it’s kg/(N·s).
Lower TSFC means better fuel efficiency.
Typical values: 0.5‑0.9 lb/(lbf·h) for turbofans.

Applications

Thrust specific fuel consumption (TSFC), TSFC = ṁ_f / T, is the fuel flow rate per unit thrust, a measure of engine efficiency. Lower TSFC means less fuel for a given thrust, leading to better range and endurance. Engineers use TSFC to compare engines, to design propulsion systems, and to predict mission performance. It is a key parameter in the Breguet equations. By reducing TSFC through advanced cycles and materials, aerospace engineers can improve aircraft efficiency and reduce emissions.

Engine selection and performance comparison
Mission performance prediction (range, endurance)
Propulsion system design and optimisation
Technology roadmapping for next‑generation engines
Economic and environmental analyses

Thrust Specific Fuel Consumption (TSFC)