MCF to MMBTU

Engineering fundamentals for gas volume and energy conversions

1. Unit Definitions

Natural gas is measured by volume (at standard conditions) and sold by energy content. Understanding the relationship between these units is essential for gas measurement, contracts, and billing.

Volume Units

Abbreviation	Name	Value
scf	Standard cubic foot	1 ft³ at standard conditions
MCF	Thousand standard cubic feet	1,000 scf
MMCF	Million standard cubic feet	1,000,000 scf
BCF	Billion standard cubic feet	10⁹ scf
TCF	Trillion standard cubic feet	10¹² scf

Energy Units

Abbreviation	Name	Value
BTU	British Thermal Unit	Energy to heat 1 lb water by 1°F
MMBTU	Million BTU	1,000,000 BTU
Therm	Therm	100,000 BTU = 0.1 MMBTU
Dth	Dekatherm	1,000,000 BTU = 1 MMBTU
GJ	Gigajoule	947,817 BTU ≈ 0.948 MMBTU

Note on "M" prefix: In oil and gas, "M" means thousand (Roman numeral), not million. MCF = 1,000 cf. "MM" means million (M × M). MMBTU = 1,000,000 BTU.

2. Conversion Calculations

Basic Conversion

Energy = Volume × Heating Value MMBTU = MCF × (HHV / 1,000) Where: HHV = Higher Heating Value (BTU/scf) MCF = Volume (thousand standard cubic feet) For typical pipeline gas (HHV = 1,020 BTU/scf): MMBTU = MCF × 1.020 MCF = MMBTU / 1.020 = MMBTU × 0.980

Quick Reference Conversions

From	To	Multiply by
MCF	MMBTU	HHV/1000 (≈1.02)
MMBTU	MCF	1000/HHV (≈0.98)
MMCF	MMBTU	HHV/1000 × 1000 (≈1,020)
MMBTU	Therms	10
MMBTU	GJ	1.055
MCF	Therms	HHV/100,000 (≈10.2)

Example Calculations

Example 1: Convert 50 MMCFD to MMBTU/day (HHV = 1,035 BTU/scf)

Energy = 50,000 MCF × (1,035 / 1,000)
Energy = 50,000 × 1.035 = 51,750 MMBTU/day

Example 2: Gas sales at $3.50/MMBTU, 100 MCF delivered (HHV = 1,020)

MMBTU = 100 × 1.020 = 102 MMBTU
Revenue = 102 × $3.50 = $357.00

3. Heating Values

Heating value is the energy released when gas is burned completely. It varies with gas composition.

HHV vs LHV

Higher Heating Value (HHV): Also called Gross Heating Value Includes latent heat of water vapor condensation Used in US gas measurement and sales Lower Heating Value (LHV): Also called Net Heating Value Excludes water vapor latent heat Used in efficiency calculations, some international markets Relationship: LHV ≈ HHV × 0.90 (for natural gas)

Component Heating Values

Component	HHV (BTU/scf)	LHV (BTU/scf)
Methane (C₁)	1,010	909
Ethane (C₂)	1,770	1,619
Propane (C₃)	2,516	2,314
n-Butane (C₄)	3,262	3,010
i-Butane	3,252	3,000
n-Pentane (C₅)	4,008	3,706
Hexane+ (C₆+)	4,756	4,403
Nitrogen (N₂)	0	0
Carbon Dioxide (CO₂)	0	0
Hydrogen Sulfide (H₂S)	637	586

Mixture Heating Value

Mixture HHV (molar basis): HHV_mix = Σ (y_i × HHV_i) Where: y_i = Mole fraction of component i HHV_i = Heating value of component i (BTU/scf) Example: 95% CH₄, 3% C₂H₆, 2% N₂ HHV = 0.95×1010 + 0.03×1770 + 0.02×0 HHV = 959.5 + 53.1 + 0 = 1,013 BTU/scf

Typical Gas Heating Values

Gas Type	HHV Range (BTU/scf)
Dry pipeline gas	1,000–1,050
Rich (wet) gas	1,100–1,400
Lean gas (high N₂)	850–950
Associated gas	1,200–1,600
LNG (regasified)	1,000–1,100
Biogas/RNG	950–1,000

4. Measurement Standards

Standard conditions define the reference temperature and pressure for volume measurement.

Common Standard Conditions

Standard	Temperature	Pressure	Usage
US Oil & Gas	60°F (15.56°C)	14.73 psia	Most US pipelines, FERC
Texas/Oklahoma	60°F	14.65 psia	Some state regulations
ISO 13443	15°C (59°F)	101.325 kPa	International
Metric (Normal)	0°C (32°F)	101.325 kPa	Some European

Correction Between Standards

Volume correction between base conditions: V₂ = V₁ × (P₁/P₂) × (T₂/T₁) × (Z₁/Z₂) Pressure correction (14.73 to 14.65 psia): V_14.65 = V_14.73 × (14.73/14.65) = V_14.73 × 1.0055 Energy is unaffected: MMBTU stays constant regardless of volume base (HHV adjusts inversely with volume)

⚠ Contract verification: Always confirm standard conditions in gas purchase/sale agreements. A 0.5% difference in pressure base equals 0.5% difference in measured volume and billing.

5. Applications

Gas Sales and Billing

Volumetric sales: Price per MCF (requires defined heating value)
Energy sales: Price per MMBTU (independent of composition)
Thermal billing: Price per therm (residential/commercial)

Wobbe Index

Wobbe Index: WI = HHV / √SG Where: SG = Specific gravity (air = 1.0) Purpose: Indicates gas interchangeability for burners Typical range: 1,310–1,390 BTU/scf for US pipeline gas

Daily/Monthly Conversions

Rate	Conversion
MMCFD to MMBTU/day	× HHV/1000 × 1000 (≈ × HHV)
MMCFD to MMBTU/month	× HHV × days in month
MMBTU/year to MMCFD	÷ HHV ÷ 365

Fuel Gas Calculations

Problem: A compressor station requires 500 HP. Estimate fuel gas at 8,500 BTU/HP-hr heat rate.

Heat input = 500 HP × 8,500 BTU/HP-hr = 4.25 MMBTU/hr
Daily = 4.25 × 24 = 102 MMBTU/day
At HHV = 1,020 BTU/scf:
Fuel gas = 102,000 / 1.020 = 100 MCF/day

References

GPA 2145 – Physical Constants for Paraffin Hydrocarbons
GPA 2172 – Calculation of Gross Heating Value
AGA Report No. 5 – Natural Gas Energy Measurement
ISO 6976 – Natural Gas Calculation of Calorific Values