How Invar 36 is priced per kilogram and how to buy it smarter

By Invar Machining editorial team· Published September 26, 2026 · How we write these guides

Invar 36 cost per kg is set mostly by nickel. The alloy is 36 % nickel by weight, nickel is traded on the London Metal Exchange and mills pass that price through as a surcharge that moves month by month. On top of that base sit the form, the size, the quantity and whether you buy from a mill or a distributor. The result is a price per kilogram several times that of 304 stainless, and a material line that typically makes up 20 to 50 % of a finished machined part. No fixed number holds for long. The quote governs.

Nickel content and the LME

Invar 36 to ASTM F1684 contains 36 % nickel, balance iron, with small limits on carbon, manganese and silicon. Iron is cheap. Nickel is not, and its price swings. Producers of nickel alloys therefore quote a base price for the alloy and add an alloy surcharge that tracks the LME nickel price, usually set monthly from the previous month’s average. When nickel rises 20 %, the surcharge follows and the cost of your bar follows it a month later.

Two consequences for a buyer. First, a quote for Invar material is valid for a short window, often 30 days or less, and a shop that quoted in one month may have to re-quote the material line in the next. Second, a fixed price agreement over a year is possible but the seller will price in the risk, so it is rarely cheaper than paying the surcharge as it comes. Some buyers with recurring volume agree a base price plus a published surcharge, which keeps the mechanism transparent.

The Invar alloy family includes Super Invar with 32 % nickel and 5 % cobalt, and Kovar with 29 % nickel and 17 % cobalt. Cobalt is more expensive than nickel and more volatile, so those alloys sit higher per kilogram and their surcharges move more.

Mill or distributor

A mill sells by the heat lot. Minimum quantities run from a few hundred kilograms to several tonnes depending on the product, the size and the mill. Lead time is measured in weeks to months because the alloy is melted, rolled and annealed to order. In exchange the price per kilogram is the lowest available and you get a single heat lot with one certificate, which matters for programs that need lot traceability. The Invar material certification guide covers what that certificate contains.

A distributor holds standard sizes on the shelf and cuts to length. You pay a premium per kilogram for the convenience plus a cut charge, and you may receive material from more than one heat lot on a larger order. For prototypes and small batches the distributor is the only practical route, and the premium is small compared with the cost of waiting for a mill run.

Source	Minimum, typical	Lead time, typical	Price per kg, relative	Suits
Mill, direct	Hundreds of kg to tonnes	8 to 20 weeks	Lowest	Production programs with known volume
Distributor, stock size	One cut piece	Days to 2 weeks	Higher, plus cut charge	Prototypes and small batches
Distributor, non-stock size	Often a full bar or plate	4 to 12 weeks	Between the two	Odd sizes when a mill run is too large
Shop’s own stock or remnant	Whatever is on hand	Immediate	Varies, ask	Small parts that fit a remnant

Typical patterns. Prices and minimums change with the market and the seller, and the quote governs. The stock and lead time planning guide covers how to time a material buy.

Bar, plate or sheet

The product form carries its own premium. Round bar in common diameters is the most produced form and the cheapest per kilogram. Plate costs more because rolling wide, thick sections yields less and the market is smaller. Thin sheet and strip cost more again because each rolling and annealing pass adds cost and the final gauge tolerance is tight. Forged blocks and special sections are quoted case by case.

Form	Price per kg relative to round bar, typical	Notes
Round bar, 10 to 100 mm	1.0	Widest availability
Round bar, above 150 mm	1.1 to 1.3	Fewer mills, longer lead time
Plate, 10 to 50 mm	1.1 to 1.4	Cut to size charges apply
Plate, above 50 mm	1.3 to 1.6	Often a mill order
Sheet, 0.5 to 3 mm	1.2 to 1.6	Sold by the sheet, not the kilogram
Strip, under 0.5 mm	1.5 and up	Coil minimums

Typical relative values, not a price list. Ask the seller for the current figure. The bar, plate and sheet guide compares the forms for machining.

Minimum cut lengths and surcharges

The price per kilogram on a distributor’s list is rarely what you pay. Add:

• A cut charge per piece plus a minimum order value.
• A minimum cut length, often 100 to 300 mm on bar, so a 40 mm long part is billed at the minimum.
• The alloy surcharge, if the list shows base price only.
• Certification charges when you ask for more than the standard mill cert, such as measured CTE for the heat lot.
• Freight, which on a heavy alloy from a distant warehouse is not small.

None of these is hidden, but they are easy to miss when comparing a per kilogram figure across two sellers. Ask for a delivered price for the exact cut sizes.

Yield and scrap

The kilograms you buy are not the kilograms you ship. A machined part is cut from a block or a bar that has to be larger than the part on every side, and the chips go into a bin. The ratio of stock mass to finished mass, called the buy to fly ratio in aerospace, runs from about 1.5 on a simple turned part to 5 or more on a pocketed plate part or a ring cut from solid.

Invar chips have scrap value because of the nickel, but a shop rarely gets more than a fraction of the purchase price back and only when it keeps the alloy segregated. For quoting purposes, treat chips as lost. The way to recover the money is to design for yield: order plate close to the finished thickness, use tube or ring stock for rings and cut several parts from one bar in the same setup. The design for machinability guide gives more examples.

How material becomes 20 to 50 % of a part price

On a machined Invar part the material line sits, typically, between a fifth and a half of the part price. Where it lands depends on the ratio of material mass to machining time.

Part type, typical	Material share of part price
Small turned spacer, 20 g finished, 40 g stock	15 to 25 %
Mirror mount from plate, 0.4 kg finished, 1.2 kg stock	25 to 40 %
Simple base plate, 3 kg finished, 4 kg stock, few features	45 to 60 %
Pocketed frame, 2 kg finished, 8 kg stock, many hours milling	25 to 35 %
Thin ring from solid plate, 0.3 kg finished, 2.5 kg stock	35 to 50 %

Typical shares for planning. The shop’s quote governs, and the Invar 36 machining cost guide explains the other lines.

The pattern is that simple heavy parts are material dominated and complex light parts are labour dominated. That tells you where to push. On a base plate, a standard plate thickness saves more than a tolerance change. On a pocketed frame, a looser tolerance or a simpler pocket saves more than any material negotiation. The Invar versus stainless steel cost guide shows the same split on the alloy the part would otherwise be made from.

Worked example, hypothetical

Take a hypothetical Invar 36 mounting block, 120 × 80 × 30 mm finished, with two pockets and six tapped holes, in a batch of 20. Assume, purely for illustration, a delivered distributor price of 60 to 90 USD per kilogram for 32 mm plate cut to size. Real prices differ by market, month and seller, and the figures below exist only to show the arithmetic.

Stock per part: 125 × 85 × 32 mm, which is 0.34 litres, or 2.74 kg at 8.05 g/cm3. Finished part after pockets and holes: about 1.9 kg. Buy to fly 1.44. Material per part at the hypothetical range: 164 to 247 USD. Add a cut charge of, say, 8 USD per piece and the material line sits at roughly 170 to 255 USD per part.

Now suppose the machining takes 2.5 h per part including roughing and finishing, the stress relief is one furnace load for all 20 and inspection is 20 min per part. At a hypothetical shop rate the labour and furnace lines might total 250 to 350 USD per part. The part price then lands around 420 to 600 USD, and material is 35 to 45 % of it. If the same block were 3 mm thinner and fit 30 mm plate without a skim on each face, the stock would drop to 2.57 kg and the material line by about 6 %. If the pockets were removed, machining time would drop but the material share would rise toward 55 %.

None of these numbers is a quote. They show the arithmetic only.

How to buy smarter

• Design to standard sizes. A finished thickness that fits standard plate with 1 to 2 mm of stock per face avoids paying for the next size up. Ask the distributor for its stock list before the drawing is final.
• Let the shop buy. Shops that cut Invar regularly know which distributor has stock and can sometimes pull from a remnant. Supplying material yourself saves the markup but moves the risk of a wrong size or a bad cert to you.
• Order for the year. A blanket order with scheduled releases lets the shop buy one heat lot at a better price and lets you hold a single certificate across releases. The minimum order quantity guide covers how shops price these.
• Nest parts. Several small parts from one bar or one plate in a single setup cut both material waste and setup time.
• Ask about remnants. For prototypes, a shop’s offcut from another job is often cheaper than a fresh cut length at the minimum.
• Do not over specify the cert. Measured CTE on the heat lot costs extra and takes time. Ask for it when the part needs it.

What to put on the RFQ

State the alloy and spec, Invar 36 to ASTM F1684 or the UNS number, the condition and the quantity, including expected annual volume if the part repeats. Say whether you will supply material or want the shop to buy it, and whether you need a single heat lot across the batch. List the certificates you need. Give the finished dimensions and let the shop propose the stock size, or state the stock size if you have already found a standard one. When you send the RFQ, we match you with up to three shops that machine the alloy and know where to source it, so each quote shows a material line you can compare. Spec references are collected on the Invar specifications page. See also the Invar 36 machining page.

Frequently asked questions

Reviewed against

• ASTM F1684, Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications
• Wikipedia, Invar

Values in this guide are typical handbook figures for planning. The mill certificate for your heat lot and the shop's quote for your geometry govern.

Keep reading

• Why Invar 36 Parts Are Costly and How Shops Price Them · Cost
• Choosing Invar Stock: Bar vs Plate vs Sheet · Materials
• Obsolescence and Long Lead Times: Planning Invar Stock Orders Around Mill Minimums · Materials
• Minimum Order Quantities and Scrap Rates on Small Invar Batches · Cost

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