--- title: Print Unit Converter｜Học viện Tri thức Mai Strategy lang: vi source: https://mindsprt.dev/vi/tools/print-unit-converter/ --- # Print Unit Converter > Designers work in points, sales in millimetres, mills in pounds. Convert across all three and see why the numbers disagree Three things trip people up when converting print units. First, there are two kinds of point: the PostScript point used in print is 1/72 inch, while the CSS pixel is 1/96 inch, so mixing them introduces a 33% error. Second, a US basis weight in pounds is not a weight but the total weight of 500 sheets at that grade's basic size, and the basic size differs per grade, which is why 80 lb cover is nearly twice as thick as 80 lb text. Pick the grade or the conversion will be wrong. Third, sheet cuts are just the full sheet halved along its long edge; the arithmetic is easy but the base sheet is ambiguous, since an untrimmed Shiroku sheet at 788×1092 and a commonly trimmed one at 760×1040 differ by 28mm. All three are handled here, with the base sheet left to you. ## How to Use 1. In Length & type, enter a value and pick From and To units; DPI also converts to pixels 2. In Basis weight to gsm, pick a Paper grade first, then fill either Basis weight (lb) or Grammage (gsm) 3. In Sheet cuts, pick a Base full sheet and read the Size (mm) for each Cut in the table 4. Treat cut sizes and weight conversions as theoretical; confirm actual stock and trim with your printer ## Method & Assumptions Length conversions are anchored on the PostScript point: 1 pt = 1/72 inch and 1 pica = 12 pt. The CSS convention of 1 px = 1/96 inch is deliberately excluded from the same table, because mixing the two is the most common source of error. Pixels sit in their own field and require a DPI, since a pixel has no physical size without one. Basis weight formula: gsm = lb × 453.59237 ÷ (500 × basic width × basic height × 0.00064516). Basic sizes use the values standard in North American paper: Bond 17×22, Text/Book 25×38, Cover 20×26, Bristol 22.5×28.5, Index 25.5×30.5, Tag and Newsprint 24×36 inches. The formula is regression-tested against published conversion charts: 20 lb Bond = 75 gsm, 70 lb Text = 104 gsm, 80 lb Cover = 216 gsm, all three matching. Sheet cuts are derived by repeatedly halving the base sheet along its long edge rather than copied from a table, with results floored to whole millimetres per trade convention. The derivation is regression-tested cell by cell against published Shiroku and Kiku cut tables. Six base sheets are offered, each labelled as untrimmed or trimmed. That ambiguity is real, and flattening it would be more dangerous than showing it. Everything runs in your browser; your inputs are never sent to a server. ## Use Cases - 10 pt converts to 3.53 mm. The same number read as a CSS pixel size would come out at 2.65 mm, a 33% difference. - 70 lb Text converts to 104 gsm, the weight of typical catalogue text stock. - 80 lb Cover converts to 216 gsm. Same number of pounds, nearly twice the thickness of Text, which is where quotes most often get misread. - An 8-up cut from an untrimmed 788×1092 Shiroku sheet is 273×394 mm. On a commonly trimmed 760×1040 sheet the same 8-up becomes 260×380 mm. - An 8-up cut from a 635×889 Kiku sheet is 222×317 mm, close to A4, which is why Kiku is often used to impose A4 work. - A 3 mm bleed at 300 DPI is 35 pixels, ready to drop into your document setup. ## FAQ ### Why does my point-to-millimetre result differ from my software? Usually because two kinds of point are in play. The PostScript point used in print is 1/72 inch; the CSS pixel is 1/96 inch. This tool uses the print convention throughout, and keeps pixels in a separate field that requires a DPI. ### Why must I pick a paper grade before converting basis weight? Because a US basis weight is the total weight of 500 sheets at that grade's basic size, and the basic size differs per grade. Text is 25×38 inches and Cover is 20×26, so the same 80 lb comes out at 118 gsm for Text and 216 gsm for Cover. A single formula would simply give the wrong answer. ### Is Shiroku 787 or 788 millimetres? Both are in use. 788×1092 is the traditional untrimmed size and 787×1092 is the metric conversion of 31×43 inches. One millimetre barely matters at cut level, but Taiwanese mills also commonly trim the full sheet to 760×1040 or 758×1060, and that gap is 28mm. All six bases are listed so you can match what your printer actually stocks. ### Can I use the cut sizes as finished sizes? No. The table gives theoretical divisions of the full sheet. Bleed, gripper and trim tolerance still come off, so the finished piece is always smaller. For exact figures, work from your printer's imposition. ### Where do these numbers come from? The basis weight formula is regression-tested against published paper conversion charts at three points. The cut sizes are derived by halving and then compared cell by cell against published Shiroku and Kiku tables. The test script lives in the repo and can be re-run. ### Are my files uploaded? No. Every conversion runs in your browser and nothing is sent to a server. ## Limitations & Disclaimer - Cut sizes are theoretical divisions with no allowance for bleed, gripper or trim tolerance, and must not be used as finished sizes. - Base sheets vary by mill. Six common ones are listed, but your printer's actual stock is what counts. - Basic sizes follow North American practice. European and Japanese systems differ, so confirm which one a quote is using before converting. - Caliper (microns or points) and ream weight are not covered; both depend on the bulk of the specific stock and cannot be derived from gsm alone. - Values are floored to whole millimetres to match trade convention, which can differ by 1mm from charts that round to nearest. Updated: 2026-08-15 · Method version: v1.0.0 --- > HTML version: https://mindsprt.dev/vi/tools/print-unit-converter/ > MINDS — 麥思印刷整合有限公司 · https://mindsprt.dev