Coal & Petcoke Quality Calculator
Convert coal and petcoke quality between AR/AD/DB/DAF bases, GCV to NCV, CV-linked price adjustment with penalties, and iron ore Fe-unit value.
Overview & methodology
Coal, petcoke and iron ore quality maths
Coal and petcoke quality is quoted on different bases — as-received (AR/ARB), air-dried (AD/ADB), dry basis (DB) and dry-ash-free (DAF) — because moisture and ash content vary with sampling and handling. Converting consistently between bases (per ISO 1928 / ASTM D3180) is essential before comparing assay results to contract specifications.
Gross calorific value (GCV) is converted to net calorific value (NCV) by deducting the latent heat of vaporisation of water formed from hydrogen combustion plus inherent moisture. Contract price is typically indexed to CV on a pro-rata basis, with bonus caps and rejection limits, alongside penalties for ash, sulphur and other deleterious elements above contractual limits. Iron ore cargoes are priced per Fe unit against an index, net of penalties for silica, alumina, phosphorus and sulphur.
Frequently asked questions
How do I convert coal GAR to NAR?
NAR (net as received) removes the latent heat of the moisture and of the water formed from hydrogen. A common approximation is NAR = GAR − 50.6 × H(ar) − 5.83 × M(ar) in kcal/kg. Always convert to the as-received basis first, then apply the gross-to-net deduction — never the other way round.
What is the difference between ADB, ARB, DB and DAF?
ARB (as received) includes total moisture, ADB (air dried) includes only inherent moisture, DB (dry) excludes all moisture, and DAF (dry ash free) excludes both moisture and ash. Converting between them is a ratio of the remaining mass fractions, so you need total moisture, inherent moisture and ash to move between bases.
How is the coal price adjusted for calorific value?
Contracts price a base CV and pro-rate the actual: adjusted price = base price × actual CV ÷ base CV, subject to a rejection limit. Ash, sulphur, moisture and size penalties are then deducted per the contract penalty table, and a bonus may apply above the base CV if the contract allows it.