How do I calculate my car's fuel efficiency in km per litre?

Fill the tank full, note the odometer or reset the trip meter, drive normally, then fill full again and read the litres off the pump. Divide the distance by the litres: km/l = distance ÷ litres. For example, 420 km on 32.5 L is 420 ÷ 32.5 = 12.92 km/l. One full-to-full cycle is enough; averaging a few tanks is more reliable.

What is a good fuel economy (km/l) for a car in Sri Lanka?

It depends on the vehicle. A small petrol hatchback like an Alto or Wagon R typically returns 16–22 km/l, a 1.3–1.8 L sedan 11–16 km/l, and an SUV or van 8–13 km/l. Three-wheelers do about 28–35 km/l and 100–150 cc motorcycles 40–55 km/l. Hybrids often beat their petrol equivalents.

How do I convert L/100km to km/l?

The two are reciprocals scaled by 100: km/l = 100 ÷ (L/100km), and L/100km = 100 ÷ (km/l). So 8 L/100km is 100 ÷ 8 = 12.5 km/l, and 20 km/l is 100 ÷ 20 = 5 L/100km. Manufacturers usually quote L/100km; Sri Lankan drivers talk in km/l. This tool shows both at once.

How much does petrol cost per kilometre in Sri Lanka right now?

Cost per km = fuel price ÷ km/l. At the current Ceylon Petroleum Corporation rate of Rs 434/L for Petrol 92, a car doing 12.92 km/l costs Rs 33.59/km. A thriftier 18 km/l car costs about Rs 24.11/km. Enter your own economy and price above for an exact figure.

Is km/l or L/100km the better way to measure fuel efficiency?

Both are correct; they answer different questions. km/l (higher is better) is intuitive for "how far on a litre". L/100km (lower is better) is linear in fuel used, so it is better for comparing savings — going from 10 to 8 L/100km saves the same fuel per 100 km whatever the distance. Cost per km, which this tool also gives, is the most practical for budgeting.

Why use full-to-full instead of the trip computer reading?

Trip-computer economy figures are often optimistic by 5–10% because of how they estimate injector flow. The brim-to-brim method measures the fuel you actually paid for against the distance you actually drove, so it reflects real running cost. Use the same pump and let it click off both times for consistency.

How do mpg figures in car reviews relate to km/l?

US and UK gallons differ, so mpg comes in two flavours. Imperial (UK) mpg = km/l × 2.824809, and US mpg = km/l × 2.352146. So 12.92 km/l is about 36.5 Imperial mpg or 30.4 US mpg. UK reviews quote the larger Imperial number; US reviews the smaller one. The calculator converts all four units together so you never mix them up.

Are the fuel prices in this tool up to date?

The default prices are the CPC retail rates from the 2026-05-30 revision (Petrol 92 Rs 434, Auto Diesel Rs 407). CPC revises prices monthly and publishes no live API, so the price field is editable — type the current pump price and every cost figure updates instantly. Last checked 2026-07-16.

Sri Lanka · Travel

Sri Lanka Fuel Efficiency Calculator — km/l, Mileage & Cost per km

Find your vehicle's real fuel economy from fill-up data, see it in km/l, L/100km and mpg side by side, and turn it into a rupee cost per km and a monthly petrol budget at today's CPC prices. No signup, no ads, sources cited below.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated Jul 16, 2026

Fuel efficiency & costkm/l · L/100km · mpg

CPC price · 2026

Distance travelled (km)

Odometer / trip-meter reading between two full tanks.

Fuel added at refill (litres)

Litres shown on the pump when you brim the tank again.

Fuel type

Default price is the CPC retail rate for this grade.

Price per litre (Rs)

From CPC notice of 2026-05-30. Edit if revised.

Fuel economy

~ Sedan range

km / litre

12.92km/l

L / 100 km

7.74L/100km

US mpg

30.4mpg

Imperial mpg

36.51mpg

Running cost at Rs 434/L

Cost per km

Rs 33.58

Cost per 100 km

Rs 3,358

Monthly commute

Rs 30,561

70.42 L / month

Annual commute

Rs 366,730

10,920 km / year

Commute budget

Distance per day (km)

Round-trip commute distance for a typical driving day.

Driving days per month

Whole days, 1–31. Skip weekends? Use ~22.

Is that good? Typical Sri Lankan ranges

Vehicle class	Typical km/l	Examples
Small hatchback	16–22	Alto, Wagon R, Vitz — light petrol city cars.
Sedan	11–16	Axio, Allion, Civic — 1.3–1.8 L petrol.
SUV / van	8–13	Vezel, Hiace KDH, Montero — heavier body.
Three-wheeler	28–35	Bajaj / TVS petrol trishaw.
Motorcycle	40–55	100–150 cc commuter bikes.

Informational real-world ranges from owner reports — not a specification. Your result depends on engine condition, tyre pressure, load and driving style.

Unit conversions use exact SI/NIST constants (1 mile = 1.609344 km, 1 Imp gal = 4.54609 L, 1 US gal = 3.785411784 L). Default fuel prices are Ceylon Petroleum Corporation retail rates. Full sources are listed under the calculator.

How it works

Fuel efficiency is just distance divided by the fuel it took. This calculator measures it the way a workshop would — the full-to-full (brim) method — and then expresses the answer in every unit you are likely to meet, before pricing it in rupees.

Economy from a fill-up. Brim the tank, note the odometer, drive normally, then brim again and read the litres from the pump. km/l = distance ÷ litres. A trip of 420 km on 32.5 L is 12.92 km/l.
Unit conversion. Every other unit is derived from km/l using exact, definitional constants — no estimation:
- L/100km = 100 ÷ km/l
- Imperial mpg = km/l × 2.824809
- US mpg = km/l × 2.352146
The mpg factors come from the exact SI definitions: 1 mile = 1.609344 km, 1 Imperial gallon = 4.54609 L, 1 US gallon = 3.785411784 L. Dividing the gallon size by the mile gives the factor.
Cost per km. cost/km = fuel price ÷ km/l, which is algebraically identical to price × (L/100km) ÷ 100 and to (price × litres) ÷ distance. The math module carries all three formulas and reconciles them, so the worked examples below tie out to the cent. Cost per 100 km is simply cost per km × 100.
Monthly and annual budget. From your commute: litres/month = (daily km × driving days) ÷ km/l, then monthly cost = litres × price, and annual = monthly × 12.

Fuel prices default to the Ceylon Petroleum Corporation retail rate for the grade you pick (from the 2026-05-30revision), but the field is editable — CPC revises prices roughly monthly, so typing the current pump price keeps every figure exact between updates. The “typical ranges” table is informational context from owner reports, not part of the calculation. This tool answers “what does my car return and cost?”; to price one specific trip by route, use the Sri Lanka Fuel Cost Calculator.

Worked examples

Petrol car — fill-up method

420 km on 32.5 L, Petrol 92 @ Rs 434/L

km/l = 420 ÷ 32.5 = 12.92 km/l
L/100km = 100 ÷ 12.92 = 7.74 L/100km
Imperial mpg = 12.92 × 2.824809 = 36.51 mpg
US mpg = 12.92 × 2.352145 = 30.40 mpg
Cost/km = 434 ÷ 12.92 = Rs 33.58/km
Cross-check: 434 × 32.5 = Rs 14,105 over 420 km → Rs 33.58/km ✓

Three-wheeler — monthly commute budget

30 km/l, 35 km/day, 26 days, Petrol 92 @ Rs 434/L

Litres/month = (35 × 26) ÷ 30 = 910 ÷ 30 = 30.33 L
Monthly cost = 30.33 × 434 = Rs 13,164.67
Cross-check via cost/km: (434 ÷ 30) × 910 = Rs 13,164.67 ✓
Annual cost = 13,164.67 × 12 = Rs 157,976

Diesel SUV — converting a manufacturer figure

Maker rates 8.5 L/100km, Auto Diesel @ Rs 407/L

km/l = 100 ÷ 8.5 = 11.76 km/l
Imperial mpg = 11.76 × 2.824809 = 33.23 mpg
Cost/km = 407 × 8.5 ÷ 100 = Rs 34.60/km
Cross-check via km/l: 407 ÷ 11.76 = Rs 34.61/km ✓ (1 cent rounding)

Frequently asked questions

Sources & references

Conversion constants are exact SI/NIST definitions and do not change. The default CPC prices were last cross-checked on 2026-07-16; the price field is editable so the tool stays correct after each monthly CPC revision.

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