How to calculate theoretical weight of ppgi coil per ton

2026/08/25

A trading manager in Uzbekistan once forwarded us a competitor's spreadsheet: three “standard” PPGI coils quoted at 5.95 tons total, with no width, no thickness, no coating weight — only an invoice number and a lump weight. Were 5.95 tons of steel actually going to arrive at the port scale? Nobody could say until unloading day. Scenarios like this are why every buyer of ppgi coil should be able to verify a theoretical weight calculation in under two minutes. The mathematics is simple, the industry conventions are few, and the protection it gives you against short-weight claims and vague quotations is immediate. Here is the complete method, illustrated with worked numbers from a real export order.

The Core Formula Every Buyer Should Know

Pondus ferri derivatur ex volumine multiplicato per densitatem; pro bobinis autem volumen redigitur ad latitudinem × spissitudinem × longitudinem.

Pondus theoricum (kg) = latitudo (mm) × spissitudo (mm) × longitudo (m) × 7.85 ÷ 1000

Combinatio millimetrorum cum metris intenda est et normata est: si latitudo in mm, spissitudo in mm, longitudo in m datur, divisio per 1000 directe kilogrammata reddit. Constanta 7.85 est densitas ferri carbonici simplicis in g/cm³. Pro bobinis PPGI, usus commercialis fere semper 7.85 retinet, quia pellicula picturae tantum 15–25 micronia per faciem addit, dum recinctio zinci intra tolerantiam substrati sita est. Emptores exacti recinctionem expresse adicere possunt — recinctio Z60 circa 0.06 kg/m², pictura vero circa 0.03–0.05 kg/m² per faciem adicit. Pro ordinibus cotidianis, formula simplex intra circiter 1.5% ponderis veri (ex ponte ponderario) cadit, quod satis prope est ut quotatio quaevis pro bobine PPGI normali examinari possit.

Studium Casus: Auditorium Ordinis Tegularum

Distributor in Kenia tria PPGI rota pro tectis corrugatis ordinavit: crassitudo 0.4 mm, latitudo 1000 mm, recinctio z60, diameter interior 508 mm. Adhibens formulam, pondus per metrum fasciculi aequale est 1000 × 0.4 × 1 × 7.85 ÷ 1000 = 3.14 kg/m. Unumquodque rota pro 3140 kg pondere theoretico citatum est, quod exacte 1000 metra per rota implicat. Distributor calculum separatim reconstruxit antequam solveret — una columna arithmetica — et citatum internam consistentiam confirmavit.

Item Ordinis	Valor
Latitudo × crassitudo	1000 mm × 0.4 mm
Pondus per meter	3.14 kg/m
Longitudo citata per rota	1 000 m
Pondus theoreticum per rota	3140 kg
Resultata ponderis ad descensum	3.121 / 3.148 / 3.152 kg
Deviation from theoretical	−0.60% / +0.25% / +0.38%

When the coils landed at Mombasa, actual net weights came in at 3.152, 3.148 and 3.121 kg — deviations of +0.38%, +0.25% and −0.60% against theoretical, comfortably inside the ±3% tolerance common in international steel trade. Because both sides had used the same formula and the same ordered dimensions, settlement took minutes instead of weeks of correspondence.

How Many Meters in a Ton of PPGI Coil?

Crassitudo	Meters per ton at 1000 mm width	Meters per ton at 1200 mm width
0.30 mm	425 m	354 m
0.40 mm	318 m	265 m
0,50 mm	255 m	212 m
0.60 mm	212 m	177 m
0,80 mm	159 m	133 m
1,00 mm	127 m	106 m
1,20 mm	106 m	89 m

Achtorum tecti hanc tabulam saepe utuntur. Ordo de 10 tonis bobinae PPGI normalis 0,4 mm latitudinis 1000 mm praebet fere 3180 metra — satis ad tectum officinae mediocris. Fabricatores tabularum apparatus domesticorum eandem tabulam in contrarium legunt: si programma tabularum 6000 metra fasciculi 0,5 mm × 1000 mm postulat, pondus bobinae ordinandae est 6000 × 3,925 = 23 550 kg, id est fere 23,5 toni. Utrumque modo conversio secundis fit, ubi formula nota est.

Theoretical vs Actual Weight: Why They Differ

Four factors create the gap between calculation and scale. First, thickness tolerance: a 0.40 mm strip rolled at 0.392 mm runs about 2% light along its entire length, often within standard rolling tolerance. Second, coating weight: heavier zinc or a thick paint film adds mass that the base-steel calculation ignores, which is why painted coils frequently weigh slightly more than theoretical. Third, edge condition: camber, out-of-square cutting and slitting burr all change the true width delivered. Fourth, scale calibration at the loading point. International practice expects ±3% between theoretical and actual for a single coil and much tighter across a full shipment; most contracts settle pricing on theoretical weight while actual weight governs the freight bill.

Five Tips to Check a Supplier's Calculation

Recompute independently: width × thickness × length × 7.85 ÷ 1000 takes thirty seconds on a phone calculator.
Ask in writing whether the quoted thickness includes paint film — commercial practice varies by market for ppgi coil.
Verify the z-grade: heavier zinc adds only grams per meter per coil weight, but it changes corrosion life and price at scale.
Cross-check coil geometry when only diameters are known: weight ≈ π/4 × (OD² − ID²) × width × 7.85, with all dimensions in meters.
Compare per-coil lengths on the packing list against measured outer diameters on arrival; a mismatch flags either measurement error or short length.

FAQ: Quaestiones Communis Responsae

Q1: Does one ton of PPGI coil include the weight of paint and zinc?

Yes — a scale weighs everything. Theoretical formulas built on 7.85 slightly underestimate painted coil; adding 2–4% for zinc coating and paint film brings most calculations within 0.5% of actual weight.

Q2: Why do suppliers quote by theoretical weight instead of scale weight?

Quia pretium stat ante productionem: pondus theoreticum derivari potest ex dimensionibus ordinatis tempore citationis, dum pondus reale solum post coitionem bobinae existit. Plurima contracta igitur reconciliantur ad tempus onerationis secundum figuras ponderis in ponte ponderario.

Q3: Num diameter interior bobinae afficit pondus, quod solvis?

Non. Diameter interior — vulgo 508 aut 610 mm — mutat tantummodo confectionem, non pondus solutum: tu pro fascia solvis, non pro oculo bobinae. Sed diameter interior momenti est pro machinis decoiliendis tuis; ideo eam specifica una cum latitudine et crassitudine.

Calculatio ponderis exacta facillima est, cum dimensiones et tolerantiae a fabbrica ad usum reguntur. Shenyang Yuanhe Steel offert bobinas PPGI, PPGL, GI et GL a pondere strati z20 usque ad z275, crassitudine 0.09–1.5 mm (usque ad 3.0 mm pro GI), secundum normas GB, JIS, ASTM et EN; haec offerta subiungitur magazzino permanenti plus quam 10 000 tonnarum in Liaoning, inspectione tripartita cum ponderatione calibrata ante onerationem, et tempore delivirationis 6–14 dierum ad clientes per totam Asiam Sudorientalem, Mediam Orientem, Asiam Centralem, Africam et Americam Meridionalem.

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