Mining & Minerals

Understanding Coal Calorific Values: 5,000, 5,500 and 6,000 kcal/kg

Compare coal energy values correctly by distinguishing GCV, NCV, GAR, GAD and units before evaluating price.

October 26, 20263 min read

Table of Contents

Figures such as 5,000, 5,500 and 6,000 kcal/kg describe energy per unit mass, but they are incomplete without a gross/net definition and analytical basis. A 6,000 GAD offer cannot be ranked above a 5,500 NCV as-received offer from the numbers alone. Ask the laboratory or supplier to report a common basis.

Gross and net describe different heat values

Gross calorific value includes the heat recovered when combustion water condenses; net calorific value excludes that latent heat. GCV and NCV therefore answer different measurement questions. A net calculation also needs composition and moisture information, not an arbitrary fixed discount from GCV.

As-received and air-dried describe sample condition

GAR means gross as received; GAD means gross air-dried. The air-dried laboratory sample and the delivered coal can contain different moisture levels. A dry-basis result is different again. Report total moisture and analysis-sample moisture explicitly when asking for conversions.

SGS publishes basis-conversion guidance and points buyers to the standards used in their contracts. Use the laboratory's documented method and agreed edition for a purchase rather than copying an online formula without checking its applicability.

Convert units without changing the basis

Using 1 kcal/kg approximately equal to 0.0041868 MJ/kg gives the illustrative conversions below. The unit conversion does not turn GCV into NCV or GAD into GAR.

kcal/kg	Approximate MJ/kg
5,000	20.93
5,500	23.03
6,000	25.12

Compare offers and contract limits

Request the same heat-value definition, moisture basis, sampling point and test method for each offer. Distinguish typical energy from guaranteed minimum and rejection values. If the contract adjusts price for energy differences, confirm the formula and whether ash, sulfur or moisture still have independent rejection limits.

For delivered-energy comparison, divide delivered currency per tonne by the agreed GJ per tonne. This compares fuel energy cost before plant efficiency. It does not account automatically for grinding, drying, ash handling or operational performance, which should be evaluated separately.

Is “5,500 coal” a complete grade?

No. The basis, impurities, moisture, sizing and application requirements are still needed. See the RFQ checklist before requesting thermal coal.

Turn the guidance into a comparable offer

Ask the proposed supplier to separate confirmed information from open items. Record the product, source country, analytical basis, shipment quantity and named delivery point on the same comparison sheet. An offer that omits one of these fields should be clarified before it is ranked against complete offers. Do not treat an indicative market description as an accepted consignment specification.

For a recurring programme, agree how changes in source or quality will be approved and how each delivery will be sampled. Keep technical approval separate from payment and freight approval, then reconcile them in the purchase contract. This helps prevent a commercially attractive offer from bypassing the receiving plant's acceptance conditions.

Duara Group assesses sourcing requirements from Kenya for African and international buyers. Origin, availability, assay, price and delivery terms require transaction-specific confirmation. Request a bulk coal quotation with your specification, metric-ton quantity, destination and delivery window.

Sources and scope

Sources reviewed on 26 October 2026. Technical guidance is a purchasing framework; the signed specification and applicable current rules control each transaction.