- Measure physical paper
- Choose coverage & protect details
- Plan exact window & outside board
- Confirm physical fit and supplier interpretation
One rectangular opening.
The model covers a flat rectangular paper sheet behind one rectangular window in a rectangular board. Width is left-to-right and height is top-to-bottom in the chosen orientation. Coverage and borders are non-negative distances. It does not model curved or multiple openings, bevel depth, cutting face, material deformation, tolerances or mounting.
Formulas you can check.
Window width = paper width − left coverage − right coverage.
Window height = paper height − top coverage − bottom coverage.
Centered left/right border = (board width − window width) ÷ 2.
Top border with extra bottom E = (board height − window height − E) ÷ 2. Bottom border = top border + E.
Custom board width = window width + left border + right border. Height follows the same rule.
The paper’s left position on the board is left border − left coverage; its top position is top border − top coverage. Checking each opposite edge rejects a sheet that would extend beyond the board. This is a placement check, not a clearance or fit specification.
Protected-area intersection.
Represent the protected rectangle by its four insets from the paper edges. Its visible width is the overlap of its left/right interval with the window interval; visible height is the equivalent top/bottom overlap. Negative overlaps become zero. Visible fraction = overlap width × overlap height ÷ protected-rectangle area.
For paper width W, protected left/right insets IL/IR and coverage CL/CR, the overlap width is max(0, min(W − IR, W − CR) − max(IL, CL)). Use the analogous formula for height. A completely enclosed rectangle is “within the mathematical opening.” A boundary match includes no practical allowance. The fraction concerns the bounding rectangle, not ink or visual importance.
Units, limits and precision.
One international inch is exactly 25.4 mm; one centimetre is 10 mm. Calculations use millimetres internally. Inputs accept non-negative decimals, simple fractions and mixed fractions. Non-zero input measurements must be at least 0.01 mm and no larger than 3000 mm. Paper, board, resulting windows and protected rectangles must be positive; window and protected-rectangle dimensions must also be at least 0.01 mm. These are software boundaries, not supplier capabilities or material limits.
Results display at most four decimal places in the selected unit. That rounding is not cutting accuracy. Unit conversions retain approximately 12 significant digits in the form, rather than repeatedly converting the rounded result. Small floating-point differences below 0.0000001 mm are treated as boundary equality for geometric checks. Real measuring and manufacturing tolerances are separate.
Independent planning, no product endorsement.
Supplier examples illustrate differing size language as checked on November 6, 2026. They are not universal overlap or fit requirements, and policies can change. Preservation references concern their stated paper/photograph contexts. Mat & Margin does not certify framing safety, recommend a board brand, sell materials or receive an affiliate payment through these links.
Measurements stay in page memory.
There is no account, upload or saved-project database. Optional analytics is described below. The calculators run in your browser. Tool-to-tool links use a URL fragment to carry dimensions locally; fragments are not included in the HTTP request. Downloaded text is created on your device. If you share that full link or file, you share the dimensions it contains.
Reloading a page without a measurement fragment restores example inputs; unsaved changes are lost. Hosting infrastructure receives ordinary page requests and may process connection data under its own service policies. We do not claim the hosting provider has no logs. External source links lead to sites with their own policies.
Optional Google Analytics
Where our regional rules require prior consent, Google Analytics stays off until you choose Allow analytics. In other regions it starts automatically unless you have opted out. Rejecting it does not prevent you from using this site. Measurements help us understand page use and improve the site; they are estimates based on browser identifiers, not a count of verified people.
| Information | How it is handled |
|---|---|
| Page use | Page addresses without query parameters or fragments, the referring site, and standard page-view and engagement events. Only predefined tool-action names may be sent; tool inputs and free text are not included. |
| Browser and network | Google receives the normal network, browser and device information needed to process an analytics request. This setup does not enable Google signals or advertising personalisation. |
| Analytics cookies | First-party Google Analytics cookies are configured for up to 180 days. They are set after permission where required, or automatically where our regional rules allow it, unless you opt out. They help distinguish browser activity. |
| Your choice | When you make an explicit choice, the optional-analytics-v1 entry in this browser’s local storage remembers it for up to 180 days. It contains the choice, its date and a version, not your tool entries. Automatic regional measurement is not saved as your consent. |
| Regional decision | Cloudflare uses the request’s coarse country code, and Canadian province where needed, to choose the regional setting. This does not use GPS or a separate IP-lookup service. We do not send this decision to Google. If it is unavailable, analytics stays off without an automatic popup; you can enable it from Analytics settings. |
Change your analytics setting
Use Analytics settings in the footer to allow or reject analytics at any time. Withdrawal stops future collection from this browser and removes accessible Google Analytics cookies set for this site. It does not delete information already processed by Google. A browser Global Privacy Control signal keeps optional analytics off.
Automatic form-interaction, site-search and other enhanced measurement are disabled. We do not send names, email addresses, account credentials, financial figures, trip notes or other form entries to Google Analytics. Query parameters and URL fragments are removed from the page address sent to it.
Ordinary hosting requests, and any separately disclosed Cloudflare measurement, are distinct from optional Google Analytics. External websites have their own privacy practices. Read how Google uses information from sites that use its services and Google’s privacy policy.
Analytics setup and this disclosure updated 7 November 2026.
Review and boundaries.
Content and formulas checked November 6, 2026. Worked cases are hypothetical and diagrams are original code-generated schematics, never photographs or proof of a real cut. The homepage studio image was generated as an illustration for this site; it does not document a frame, artwork or measurement we handled. Its role is visual context. Material shadows on diagrams are illustrative and do not certify physical depth or fit. Tests can verify calculation behavior under specified inputs; they cannot establish material quality, real-world manufacture or user acceptance. Confirm the current final specification with your supplier before an irreversible order.
Sources & scope
Checked November 6, 2026. Supplier policies are examples of that supplier’s wording, not universal specifications. Geometry and worked examples are our own derivations; see method and limits.
- Frame Destination — standard and custom mat openings
- Frame It Easy — measurements help
- Frame It Easy — measuring artwork
- Frame It Easy — measuring a picture frame
- Logan — border calculator and layout parameters
- NIST — SI units of length
- Library of Congress — preservation matting and framing
- NEDCC — matting and framing works on paper and photographs
Source: https://matandmargin.com/method/