GAR to NAR Coal Calculator: Quality & Price Adjustment
Convert Coal GAR to NAR and ADB. Calculate settlement price adjustments based on calorific value, moisture, and ash vs contract specs.
Overview & methodology
Numerical Example: Coal CV Price Adjustment
Calculation: (Base Price × Actual CV) / Base CV. Penalties apply for ash/sulphur exceeding limits.
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.