Thrust-specific fuel consumption (TSFC) is the fuel mass flow rate divided by the net thrust produced. It is the standard efficiency metric for jet, turbofan, and ramjet engines. A lower TSFC means the engine produces more thrust per unit of fuel — modern high-bypass turbofans achieve TSFC around 14–16 g/kN·s at cruise.

Power-specific fuel consumption (PSFC) is the fuel mass flow rate divided by the shaft power output. It is used for turboprop and piston engines where the useful output is mechanical power rather than jet thrust. Typical PSFC for a modern turboprop is 60–80 g/kW·h.

Why does SFC change with altitude and speed?

SFC varies with throttle setting, altitude, and Mach number. Turbofan engines are most efficient at high-altitude cruise where air is cold and dense air mass flow is managed well. TSFC generally decreases as bypass ratio increases, which is why modern wide-body engines use very high bypass ratios (10:1 or more).

What units are used for TSFC?

The metric unit is grams per kilonewton-second (g/kN·s), also written mg/N·s. The imperial unit is pounds-mass per pound-force per hour (lb/lbf·h), commonly abbreviated lbm/(lbf·h). Conversion: 1 lb/lbf·h ≈ 28.325 g/kN·s.

What is a good TSFC for a modern turbofan?

High-bypass turbofans used on commercial airliners (e.g. CFM LEAP, GE9X, Trent XWB) achieve cruise TSFC of 14–17 g/kN·s (0.49–0.60 lb/lbf·h). Military low-bypass afterburning turbofans in dry thrust typically run 20–25 g/kN·s. Older turbojet engines with no bypass could exceed 45 g/kN·s.

Specific Fuel Consumption Calculator

Name: Specific Fuel Consumption Calculator
Availability: InStock
Author: Nham Vu

Enter fuel flow rate and thrust (or shaft power) to compute thrust-specific (TSFC) or power-specific (PSFC) fuel consumption in metric and imperial units.

Engine Parameters

Calculation Mode

TSFC: fuel flow ÷ thrust. Used for jet and turbofan engines.

Fuel Flow Rate

Net Thrust

Quick Examples

Result

Enter fuel flow and thrust (or power) values to compute SFC.

SFC Reference — Common Engines

Engine	TSFC (g/kN·s)	Condition
CFM LEAP-1B	14.9	Cruise (est.)
GE9X-105B1A	14.3	Cruise (est.)
CFM56-7B27	17.0	Cruise
Trent XWB-97	15.0	Cruise (est.)
J79 (F-104)	23.0	Max dry thrust
PT6A-65 (turboprop)	— (PSFC)	~73 g/kW·h

Summary

Enter fuel flow rate and thrust (or shaft power) to compute thrust-specific (TSFC) or power-specific (PSFC) fuel consumption in metric and imperial units.

How it works

Select the calculation mode: TSFC (jet/turbofan) or PSFC (turboprop/piston).
Enter the engine fuel flow rate and select the unit (kg/h, lb/h, g/s, etc.).
For TSFC: enter thrust in kilonewtons or pound-force.
For PSFC: enter shaft power in kilowatts or horsepower.
Results appear instantly in both metric and imperial SFC units.
Compare your result against the reference table of common engines.

Use cases

Evaluate fuel efficiency of turbofan engines during preliminary design.
Compare SFC across different engine types and generations.
Convert between metric (g/kN·s) and imperial (lb/lbf·h) TSFC units.
Estimate fuel burn for a given thrust level over a flight segment.
Validate engine performance against published manufacturer data.
Assess turboprop or piston engine efficiency for general aviation.
Use in aerospace engineering coursework and exam problems.
Quick cross-check during engine selection for a new aircraft design.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu