Solar Wafer Sizes Explained: M10 vs G12 vs G12R (182 mm, 210 mm and Rectangular)

What the names mean

A solar wafer's format is its face size. For most of the last decade the industry has used letter-and-number shorthand rather than millimetres: M for formats in the line that began with the 156 mm M2 wafer, G for the larger formats that followed. A 2021 TaiyangNews overview listed the sequence as M2 (156.75 mm), G1 (158.75 mm), M6 (166 mm), M10 (182 mm) and G12 (210 mm).

Three formats matter today. M10 is a 182 mm square; PV Tech's report on the 2026 ITRPV roadmap gives it as 182.0 × 182.0 mm. G12 is a 210 mm square, given as 210.0 × 210.0 mm. G12R, often written 210R, is a rectangle that keeps one 182 mm side and stretches the other to 210 mm. Smaller rectangular variants exist too, built around the same 182 mm width.

• M10: 182 × 182 mm square
• G12: 210 × 210 mm square
• G12R / 210R: about 182 × 210 mm rectangle
• M6 (166 mm) and older formats: phased out of production by 2025, according to ITRPV 2026

How the industry settled on 182 and 210

Wafer size grew in steps because a larger wafer puts more watts through each cell, module and production step. By 2020 that growth had become a problem. pv magazine reported in June 2020 that several sizes larger than M2 were competing in the market, and that Zhonghuan Semiconductor had introduced a 210 mm wafer in 2019, the largest the industry had seen.

The answer was a standards effort. On 24 June 2020, LONGi announced that seven companies, including JA Solar, JinkoSolar, Canadian Solar and LONGi itself, had agreed on a 182 mm × 182 mm wafer, M10, and urged the industry to adopt it. Their stated reason was that the lack of a common size raised costs across the supply chain and complicated coordination between upstream and downstream makers. G12 continued in parallel, and for several years the market ran on these two squares, with TaiyangNews citing CPIA figures that showed M10 and G12 together at under 5% of the market in 2020 before taking over.

Why rectangular wafers took over

Square formats still produced modules of many sizes, which complicated mounting structures, packaging and shipping. In July 2023, TaiyangNews reported that nine manufacturers, among them Canadian Solar, JA Solar, JinkoSolar, LONGi, Trina Solar and Tongwei, had agreed on a mid-format module of 2,382 × 1,134 mm built with rectangular wafers, and backed the CPIA module-dimension specification T/CPIA 0003-2022.

The rectangle is what makes that module size work. A 182 × 210 mm wafer is cut into two 105 × 210 mm half-cells, and 66 of those fill the standard module, according to the same report. Each cell gets more area than an M10 half-cell without forcing the module to the full G12 width. TaiyangNews, describing Astronergy's 210R module in January 2024, reported benefits in transport and handling, about 15.6% more active area for the same number of cell slices, and 4.3% better container loading versus its M10 products. Those are one manufacturer's figures for one product, but they show why the format spread.

Where formats are heading

The 2026 ITRPV roadmap, reported by PV Tech in June 2026, describes a wafer market that has standardised around M10 and G12 and their rectangular variants. It projects that G12 and G12R will cover about 76% of the market over the ten-year horizon, that formats larger than G12 will approach 20%, that rectangular M10 formats will keep some share, and that standard square M10 will phase out entirely.

Format is not the only dimension moving. The same report says minimum as-cut thickness keeps falling across all formats, with no significant difference between M10 and G12 for n-type wafers, and G12 wafers for back-contact cells expected to reach 110 µm. For a wafer buyer, that means a format specification and a thickness specification now have to be written together.

What format means upstream: the ingot

A wafer's face is a slice through a squared ingot, so the format a plant targets sets the crystal it has to grow. The diagonal of a full square is its side times the square root of two: about 257 mm for a 182 mm square and about 297 mm for a 210 mm square, and about 278 mm for a 182 × 210 mm rectangle. Mono wafers are usually pseudo-square, with slightly rounded corners, so the ingot can be a little smaller than the full diagonal, but the order holds. G12 needs the widest ingot; G12R sits between G12 and M10.

That has practical consequences. Ingot diameter is set in the Czochralski puller by the hot zone, the crucible size and the growth recipe, so a grower specified around M10 may not grow G12 ingots without a hot-zone and crucible change. Squaring, brick grinding and the wire-saw set-up are also format-specific. Indian cell lines already show the mix: pv magazine India reported in April 2026 that Reliance's first HJT cells on ALMM List-II were 210 × 105 mm half-cells, a G12-class geometry.

• Name the target format, or formats, before specifying crystal growers and hot zones
• Check whether growers, crucibles and squaring equipment can move between M10-class and G12-class diameters
• Write format, thickness and corner geometry into the wafer specification together
• Confirm the formats that target cell customers are buying, not the ones a brochure lists

Why it matters for India's wafer build-out

India's ingot and wafer capacity is being planned now, ahead of ALMM List-III, which PIB says is proposed to apply to ingots and wafers from 1 June 2028. A plant ordered today will sell into a market that ITRPV expects to be dominated by G12-class and rectangular formats for most of its life. Choosing format flexibility at the puller and wafering stage is therefore a commercial decision as much as an engineering one.

This guide is general awareness, not a sizing recommendation. Format, thickness and geometry limits depend on the cell architecture and the customer, and should be validated with target cell makers and equipment suppliers before a line is specified.