Accuracy and limitations

Every output on this site is a mathematical consequence of the values you entered. The site cannot know whether those values are the right ones, and it never inspects the object, drawing, print or space they describe.

• Inputs govern outputs. A wrong unit, a transposed digit or a mis-measured reference produces an exactly computed wrong answer.
• Display rounding is not the calculation. Internal values are exact fractions; what you read may be rounded or truncated for legibility, and truncation is marked. Re-entering a rounded figure by hand into a later step can shift the result.
• Measurement uncertainty carries through. Reading a ruler to the nearest millimetre, or a caliper to the nearest tenth, sets a floor on how meaningful the trailing digits of any result can be.

Exact arithmetic is a narrower claim than a correct real-world answer. The engine is designed to compute the reported values directly from the values supplied using the documented arithmetic; it guarantees nothing about the physical situation.

Uniform geometric scaling also does not respect how things are made. Threads, fasteners, bearings, gears, press fits, electrical components, wall thicknesses and load-bearing members do not survive being multiplied by a factor, even when the arithmetic is impeccable.

The drawing, architectural and print calculators work from what you tell them about a drawing. They cannot see the sheet.

• A digital or printed drawing may already have been resized by fit-to-page printing, a different paper size, photocopying or a PDF export, so the scale printed on it may no longer be the scale of the paper in front of you.
• Written dimensions, dimension strings and the governing specification take precedence over any measurement scaled off a drawing, and over any figure this site produces from one.
• Output here is not construction verification, not a substitute for a set-out or survey, and not a check that a drawing is current, approved or complete.

Nothing here is engineering certification, calculation of record, or a design check. The site does not evaluate structural adequacy, load paths, stress, deflection, fatigue, stability, mechanical fit, electrical suitability, thermal behaviour, code compliance or safety. A geometric result says how big something becomes, never whether it will work or whether it is safe.

• Bounding-box fit is not printability. Fitting inside a build volume says nothing about adhesion, overhangs, supports, minimum feature or wall thickness, warping, elephant's foot, nozzle diameter, layer height or whether the mesh is manifold at all.
• The volume multiplier is geometry, not filament. Scaling length by k multiplies solid volume by k³. Actual material use depends on wall count, infill pattern and density, supports, brim or raft, orientation, extrusion width and flow, so it does not follow the k³ figure.
• Slicer percentages act on their own model. The slicer scales the mesh as it reads it, including any unit interpretation it applies on import; verify the resulting dimensions in the slicer before printing.

The calculators compute nominal geometry. Unless you explicitly enter it as a value, nothing accounts for tolerances and fits, kerf and cut loss, bend allowance or springback, mould shrinkage or thermal expansion, machining allowance, tool radius, stock sizes, grain or fibre direction, surface finish or the behaviour of the material. Nominal geometry is where a production drawing starts, not where it ends.

• A scaled map distance is a straight-line distance at the map's stated scale. It is not route distance, travel distance, or distance over terrain, and slope makes real ground distance longer than the map suggests.
• Map scale is only nominal across a sheet: projection, latitude, sheet distortion and reproduction all affect it, and small-scale maps generalise features rather than reproducing them.
• The site does not assess the accuracy, currency or authority of the map you measured. It is not for navigation, and it does not establish boundaries, ownership or legal position.

Documented conventions differ by domain, manufacturer, era and region, and the same nominal scale can be implemented differently by different bodies. When a calculated scale lands near a documented one, the site reports both and states the difference; the nearest match is a comparison and is not automatically the official standard, nor evidence that a model conforms to it. Reference entries carry a source and a check date, and the published standard governs. See common scales for the dataset and its sources.

Correcting a print mathematically requires that a single uniform factor describes what went wrong. Often it does not.

• If the two axes disagree, the distortion is non-uniform and one uniform percentage cannot fix it. The calculator reports the disagreement rather than averaging it into a plausible-looking wrong answer.
• The site cannot diagnose the cause. Fit-to-page settings, driver scaling, paper size mismatch, margins and non-printable areas, scanner feed error, lens or platen distortion, PDF page-box handling, and paper stretch after printing all look similar in the numbers.
• Correcting a copy compounds whatever the copy already did. Where the source file exists, starting again from that source at 100% is generally preferable to repeatedly correcting a derivative, provided the source itself is correctly configured for that output. Any correction should still be verified by measuring the new output.

• The solver tests axis-aligned bounding boxes with orthogonal (90°) rotations inside an empty rectangular space. It is not arbitrary three-dimensional packing, arbitrary-angle placement, or nesting of real shapes.
• Real obstructions are outside the model: handles, feet, plinths, skirting, door swings, doorways, corridors, stair turns, ceiling slopes, pipework, and the space needed to manoeuvre an object into position rather than to occupy it.
• A reported fit is a geometric statement only. It does not establish required clearances, ventilation or service access, egress or fire-safety compliance, load capacity of a floor or shelf, or that the object can be made at that size.

Reference conventions are sourced from published materials where an identifiable source is available. Entries labelled Common practice are included as practical reference values and do not claim a published standard. Source information and a Last verified date are shown with the reference data where applicable. Standards get revised, source documents move or disappear, and fields and jurisdictions differ in what they treat as standard practice. Entries may therefore be incomplete or out of date, and the issuing body's current publication always governs over the summary shown here. Corrections with a verifiable source are the most useful thing you can send.

You are welcome to use SnapScaleCalc in professional work, on the understanding that it is a geometry tool and that responsibility for the result stays with you.

Nothing on this site is engineering, architectural, surveying, construction, navigation, legal or safety advice. The terms of use set out the warranty and liability position; the methodology sets out exactly what each calculation does.

If a result looks wrong, tell us: the page, the values entered with units, the result shown and the result expected, to snapscalecalc@proton.me. Engine corrections take priority over everything else here.