Fuel combustion heat energy calculator is developed for calculation of heat energy (heat power) that is released during combustion of specified fuel for known fuel flow rate. Calculator is also suitable for inverse calculation of fuel flow rate for known heat power.

- Calculation of fuel flow rate for given heat energy (heat power). This is the case when you want to know how much fuel is required to produce specified heat energy - power. For this calculation type select Q/G in Calculation type section.
- Calculation of heat energy (heat power) created from combustion of specified fuel flow rate. This is the case when you know fuel flow rate and you want to know how much heat energy that fuel can create during combustion. For this calculation type select P in Calculation type section.
- Calculation of fuel heat value for given heat power and flow rate. This is the case when you want to check the heat value (or quality of fuel) based on the specified flow rate and released heat energy - power. For this calculation type select HV_V in Calculation type section.
- Flow rates can be entered as mass or volume flow rate. If you provide density value, flow rate that is not entered will be calculated.

In Selection section you can select values to input. Not selected values will be calculated. You select between:

- volume or mass flow rate (q or w)
- power or actual power (P or P1)
- lower (nett) or higher (gross) heat value (HV_V or HV_G)

In Omit section you can choose not to use and therefor not to enter density - ρ or efficiency - η.

In Report section you have instant calculation report for input values. From there you can copy/paste report to your text editor.

- Fuel flow rate calculation
- Heat power calculation
- Fuel heat value calculation
- Input values selection
- Select if fuel density is needed and available in calculation or not
- Select if energy conversion efficiency is needed in calculation or not
- Select unit of measure (metric and imperial units are available)
- View results in report view and copy/paste report to your text editor
- Find nett (lower) and gross (higher) heat values and densities for some common fuels

- q - Volume flow rate
- Fuel flow rate in terms of units of volume per unit of time
- ṁ - Mass flow rate
- Fuel flow rate in terms of units of mass per unit of time
- P - Power - heat power
- Energy created during combustion in unit of time
- P1 - Actual power
- Useful heat energy - power after reduction due to energy losses in energy conversion from combustion heat to, for example, hot water heat energy
- HV_V - Heat value
- Heat energy created during combustion in units of volume
- HV_G - Heat value
- Heat energy created during combustion in units of mass
- ρ - Density of fuel
- This value is only required if you want to calculate flow rate or heat power in different units (as per unit of mass or volume). You can select not to use this feature by selecting ρ in Omit section.
- η - Efficiency
- Energy losses coefficient ratio between actual heat power and combustion heat power that represents efficiency of energy conversion.

Efficiency coefficient is used to represent losses in energy conversion from combustion energy to energy available for end use like hot water heat energy from boiler. If you have specified hot water heat energy demand P1 and if you know boiler efficiency - η, calculator gives you required actual heat power from combustion like P1/ η. You can select not to use this feature by selecting η in Omit section.