Two Chinese foundry reference sheets list gray iron EXW at 0.56–0.69 USD/lb (1.23–1.52 USD/kg) and ductile iron at 0.61–0.67 USD/lb (1.34–1.48 USD/kg) across 0.5–1,000 kg weight bands, with the per-pound and per-kilogram numbers internally consistent at the 1 kg = 2.2046 lb ratio [S1][S2].
The kilobuck per-ton figure printed in the same tables (1,230–1,520 USD/ton for gray iron, 1,340–1,480 USD/ton for ductile) is simply the per-kg rate multiplied by 1,000, so a buyer can move freely between the three units; the unit choice matters only when weight-break thresholds in a quote are quoted in one system and the buyer's MRP system tracks the other.
Unit conversion and the 2.2046 ratio
At the standard SI conversion of 1 kg = 2.20462 lb, any USD/kg figure multiplies by 2.20462 to give USD/lb, and any USD/ton figure divides by 1,000 to give USD/kg. A 1.35 USD/kg gray-iron price therefore equals 1.35 × 2.20462 = 2.976 USD/lb gross, and 1,350 USD/ton on a metric-ton basis [S1]. The two foundry tables confirm this internally: Dandong lists 0.61 USD/lb next to 1.35 USD/kg for the 2–5 lb (1–2 kg) gray-iron band, and Yide lists 0.63 USD/lb next to 1.38 USD/kg for the same 0.5–2 kg band, a 2.19× multiplier in both cases [S1][S2].
Buyers specifying castings for North American OEM programs often see quotes in USD/lb because pattern-shop tooling and inbound scrap are priced in avoirdupois, while European and Asian procurement teams work in USD/kg and USD/MT. The price itself does not change at the conversion; what changes is which weight threshold triggers the next price break, and how a 1.5% tolerance on a 200 kg casting reads when the tolerance is given in pounds (4.85 lb) versus kilograms (3.0 kg).
Grey iron and ductile iron price bands by weight
Gray iron on EXW terms runs 0.56 USD/lb (1.23 USD/kg, 1,230 USD/ton) in the 5–100 lb (2–50 kg) sweet spot and steps up to 0.61–0.63 USD/lb (1.35–1.38 USD/kg, 1,350–1,378 USD/ton) for the 2–5 lb (1–2 kg) and 100–2,000 lb (50–1,000 kg) bookends, per Dandong and Yide reference tables [S1][S2]. Ductile iron carries a 5–10% premium over gray at every weight break, sitting at 0.61–0.62 USD/lb (1.34–1.36 USD/kg, 1,337–1,364 USD/ton) in the 5–100 lb band and 0.66–0.67 USD/lb (1.46–1.48 USD/kg, 1,456–1,481 USD/ton) at the small and large extremes [S1][S2].
Yide's process-mix breakdown for the same gray-iron parts shows green sand at 0.58–0.61 USD/lb, resin sand at 0.65–0.69 USD/lb, and shell molding at 0.72–0.76 USD/lb, with ductile iron on green sand at 0.74–0.78 USD/lb [S6]. That is a 0.14–0.18 USD/lb spread (0.31–0.40 USD/kg) attributable purely to molding process on otherwise identical ASTM A48 / A536 grades, a number that should sit on every buyer's should-cost sheet before they accept a quote [S6].
How foundry process and material grade move the price
Switching from green sand to shell molding costs roughly 0.14 USD/lb (0.31 USD/kg) on a gray-iron part, and switching from gray iron (ASTM A48, DIN 1691, EN 1561) to ductile iron (ASTM A536, DIN 1693, EN 1563) costs another 0.05–0.10 USD/lb (0.11–0.22 USD/kg) on the same pattern [S1][S2][S6]. Stepping up to cast carbon steel (C40) on green sand moves the line to 1.04–1.22 USD/lb (2.30–2.70 USD/kg), roughly 2× the gray-iron benchmark, and stainless steel AISI 316 sand-cast parts run 2.00–2.12 USD/lb (4.42–4.68 USD/kg), about 3.6× gray iron at the same weight [S3].
Investment-cast carbon steel at 3.08–3.44 USD/lb (6.80–7.60 USD/kg) and investment-cast 316 at 4.17–4.59 USD/lb (9.21–10.15 USD/kg) define the high end of the EXW range a buyer will see on a 0.1–50 kg RFQ [S3]. Resin sand and shell molding for steel push those numbers even higher because of the refractory and binder chemistry, which is why sand cast is still the default for steel parts above 10 kg unless tolerances or surface-finish specs demand otherwise. For a practical read on how a foundry's pattern and heat numbers are stamped into the part itself, see cast iron pattern numbers vs heat numbers.
What drives the per-kg number beyond material and process
Seven factors move a USD/kg figure independently of the metal itself: material grade, casting weight, design complexity, casting process, post-cast machining, order quantity, and the prevailing scrap/energy/labor market [S5]. Small castings under 1 kg carry a per-kg premium of 0.12–0.15 USD/kg (0.27–0.33 USD/lb) over the 5–50 kg band because pattern cycle time, pouring labor, and inspection scale with piece count rather than mass [S1][S2][S5].
Complex parts needing multi-part molds or internal sand cores add labor and tooling amortization on top of material, and CNC machining on critical features can add 0.40–1.20 USD/lb (0.88–2.65 USD/kg) to the finished-part cost, depending on feature count and tolerance class [S5]. Scrap iron at the foundry gate trades at 0.03–0.04 USD/lb for light shred and 0.06–0.08 USD/lb for heavy scrap as of April 2026, which is roughly 1/10th the gray-iron casting price, so a 10% yield loss at the foundry already equals the entire scrap value of the in-gate material [S7].
US and historical context for the per-pound benchmark
North American job-shop gray iron (ASTM A48 class 30–40) in simple shapes historically priced between 1.00 and 2.00 USD/lb on a net-snagged basis for repeat, high-volume work, with thermal stress relief adding 0.25–0.30 USD/lb (last quoted in 2008, pre-energy-shock pricing) and a general rule that getting below 3.50 USD/lb required matched patterns, multi-impression tooling, and ton-scale annual volume [S4]. The 2008 anecdote also notes that a 2,000 lb set of castings in the USA could run 6,000–8,000 USD before machining, which works out to 3.00–4.00 USD/lb gross, consistent with the small-lot US market in that period [S4].
Those 2008 numbers translate to roughly 5.50–7.30 USD/kg at the same ratio and bracket the high end of what Chinese sand-cast carbon steel (C40) sells for today at 2.30–2.70 USD/kg, illustrating how much global gray-iron and low-carbon-steel casting supply has shifted toward Chinese, Indian, and Southeast Asian foundries over the last 18 years [S3][S4]. The Practical Machinist thread also flagged that paperwork and per-pour certs add cost beyond the base pour, a real line item that does not show up on an EXW price sheet [S4].
Putting the units side by side: which one to quote
For gray iron sand castings, the all-in 2026 EXW band is 0.56–0.76 USD/lb, 1.23–1.68 USD/kg, and 1,230–1,680 USD/ton, and the only number that changes between them is the unit printed on the PO [S1][S2][S6]. For ductile iron the equivalent band is 0.61–0.85 USD/lb, 1.34–1.88 USD/kg, and 1,340–1,880 USD/ton once shell-mold ductile is included [S1][S2][S6]. For cast carbon steel (C40) sand cast the band is 1.04–1.27 USD/lb, 2.30–2.80 USD/kg, and 2,300–2,800 USD/ton, and for AISI 316 stainless sand cast it is 2.00–2.12 USD/lb, 4.42–4.68 USD/kg, and 4,420–4,680 USD/ton [S3].
The right unit to quote is the one that matches the buyer's MRP system and the foundry's price-break thresholds. North American OEM buyers usually see the cleanest should-cost model in USD/lb with weight breaks in pounds, while European and Asian procurement teams get a cleaner read in USD/kg with metric weight breaks. Eight considerations besides unit selection, including design, quantity, machining, and market conditions, drive the final landed cost regardless of which unit is printed on the quote [S5][S8]. When the two sides disagree on unit, fix the unit first, then negotiate the number; converting late invites rounding errors on every weight-break threshold.
The underlying component specifications are covered under cast iron, casting aux, and casting ladle.