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
NAR (net as received) is estimated from GAR (gross as received) by subtracting the latent heat carried by total moisture: NAR ≈ GAR - (50.6 × total moisture %). This is the widely used industry approximation for thermal coal specifications; the definitive determination follows ISO 1928. State the moisture basis (as received) and the result unit (kcal/kg) when you present the number.
This is an approximation, not the ISO 1928 method.
Numerical Example: GAR to NAR Worked Example
Indonesian thermal coal, GAR 4,200 kcal/kg at 32% total moisture.
Real contract values also adjust for ash, hydrogen and sulphur.
Indicative thermal coal specifications
| Origin | Typical GAR (kcal/kg) | Typical total moisture % | Typical NAR (kcal/kg) | Typical sulphur % |
|---|---|---|---|---|
| Indonesian | 3,800 to 4,600 | 30 to 38 | 2,200 to 3,000 | 0.2 to 0.6 |
| South African (Richards Bay) | 5,500 to 6,000 | 8 to 12 | 4,900 to 5,500 | 0.6 to 1.0 |
All values are indicative ranges, not live quotes. Verify against the cargo certificate of analysis.
Numerical Example: Coal CV Price Adjustment
Calculation: (Base Price × Actual CV) / Base CV. Penalties apply for ash/sulphur exceeding limits.
Method note: calculations run in your browser using the formulas and published rule books cited on this page. Results are free estimates for planning, with no login required, and should be confirmed with your bank, broker or the official source before you commit.
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.
Is this GAR to NAR conversion the ISO 1928 method?
No. The calculator uses the widely used industry approximation (NAR ≈ GAR − 50.6 × total moisture %) for quick estimates. The definitive determination of calorific value follows ISO 1928 laboratory methods, and contract settlement should rely on the certificate of analysis.