Fuel Flow Rate Calculator

Calculating Engine Fuel Consumption Rate

The fuel flow rate tells you how much fuel an engine consumes per unit time. This is critical for: fuel tank sizing, trip range calculations, engine performance analysis, and comparing fuel efficiency between engines.

The Fuel Flow Rate Formula

Fuel Flow (L/hr) = Power (kW) × BSFC / (Fuel Density × 1000)

Where:

• BSFC = Brake Specific Fuel Consumption (g/kWh) — from engine specifications
• Fuel density: petrol ~740 g/L; diesel ~850 g/L; jet fuel ~800 g/L

For petrol engines: BSFC ≈ 250–350 g/kWh at optimum; diesel engines: 195–230 g/kWh.

Simplified for vehicles: Fuel flow (L/hr) = Speed (km/hr) × Consumption (L/100km) / 100

Practical Examples

Example 1 — Diesel generator: 100kW output, BSFC = 215 g/kWh, diesel density 850 g/L. Fuel flow = 100 × 215 / (850 × 1000) × 1000 = 25.3 L/hr. At full load 8hr/day for 30 days: fuel needed = 25.3 × 8 × 30 = 6,072 litres/month.

Example 2 — Car at highway speed: 120 km/hr, 6 L/100km. Fuel flow = 120 × 6 / 100 = 7.2 L/hr.

Example 3 — Marine engine: 300 HP (224 kW) petrol engine at 80% load (179 kW), BSFC = 300 g/kWh, petrol density 740 g/L. Fuel flow = 179 × 300 / (740 × 1000) × 1000 = 72.6 L/hr.