How does a scale calculator work?
The scale of a drawing represents the ratio between the dimensions on paper and the actual dimensions. For example: scale 1:50 means that 1 unit (like 1 cm) on the plan corresponds to 50 units (50 cm) in reality. Common scales in construction and architecture are 1:20, 1:50, 1:100, and 1:200. Our scale calculator helps automatically convert these ratios.
How do you calculate the scale of a drawing?
When you want to enlarge or reduce a plan on a copier or plotter, you calculate the enlargement factor by dividing the current scale by the desired scale.
From scale 1:100 to 1:50
When you have an existing plan at a 1:100 scale and want to enlarge it to 1:50, the calculation is as follows: 100 / 50 = 2. You must therefore print or copy the original document at 200%. The image thereby becomes twice as large.
From scale 1:50 to 1:100
Do you want to convert a large plan at 1:50 to an overview plan at 1:100? The calculation is then: 50 / 100 = 0.5. In this case, you print the document at 50%. The result is a plan that is half the size.
What happens to the scale when you print from A1 to A3?
Often large technical drawings (A1 or A0) are reduced to A3 for easier distribution in a meeting or on site. ISO paper sizes are structured so that each step smaller (e.g., from A1 to A2) means halving the area. However, the linear reduction between two steps is the square root of 2 (approximately 1.414).
When you go from A1 to A3 (two steps smaller), you reduce the document linearly to exactly 50%. If the original A1 plan has a scale of 1:100, then the scale of the printed A3 plan becomes 1:200.
Common scales in building plans
- 1:10 to 1:20: Construction details and interior finishing.
- 1:50: Detailed floor plans and sections where techniques and layout are visible.
- 1:100: General building plans and architectural drawings for building applications.
- 1:200 or 1:250: Overview plans and site plans of buildings.
- 1:500: Situation plans or terrain plans.
Quick Reference Table: Scale Conversion
| Original Scale | Desired Scale | Print Percentage |
|---|---|---|
| 1:200 | 1:100 | 200% |
| 1:100 | 1:50 | 200% |
| 1:100 | 1:200 | 50% |
| 1:50 | 1:100 | 50% |
| 1:50 | 1:20 | 250% |
| 1:20 | 1:50 | 40% |
How to determine the scale of an unknown plan?
When the scale is missing or incorrect (e.g., after incorrect printing), you can calculate it yourself by measuring a known distance on the plan and comparing it with the real distance. The formula is simple: real distance / distance on drawing. Example: do you measure 50 mm on paper for a wall that is 5 meters in reality? Then the scale is (5000 mm / 50 mm) = 1:100.
How to determine which paper size you need?
If you know the real dimensions of your project (e.g., 50 meters wide) and the desired scale (e.g., 1:100), you can calculate the required drawing area (500 mm). By taking into account white margins all around (e.g., 10 mm), the tool can calculate that the smallest ISO format in which this fits is A1 (841 x 594 mm).
How to set the scale in an AutoCAD viewport?
In AutoCAD, you usually draw in 'model space' at full size (1:1). To print the plan at a specific scale on paper ('paper space'), you must set the viewport scale correctly. You do this with the ZOOM XP command. Our AutoCAD calculator calculates exactly which XP value you need, taking your drawing units into account (e.g., model in cm, paper in mm).
How to measure a distance on a PDF building plan?
With our built-in PDF tool, you can measure distances directly in the browser without expensive software. Load the PDF, select the calibration tool, and draw a line over a known distance. Enter the real distance to establish the scale of the document. After that, you can measure unlimited new distances with the measurement tool.
Practical Guide: Printing Building Plans and Technical Drawings to Scale
Calculating the right scale is only the first step; the real challenge is achieving a 100% accurate print on paper. For architects, engineering firms, and contractors, modern CAD plotters are engineered to reproduce sharp vector lines and details accurately to scale. Within this category, the reliable HP DesignJet series remains the industry standard for compact to mid-volume A1 and A0 printing.
When dozens of plan revisions need to be printed and distributed to site managers daily, standard plotters often fall short on speed. For demanding construction companies and centralized reprographics departments, the HP PageWide XL series delivers unmatched production speeds with instantaneous drying and low per-page costs.
Unsure which printing solution best matches your CAD workflow (AutoCAD, Revit) and print volume? As a dedicated large format printer company and authorized HP plotter dealer in Belgium, Europlan provides tailored advice, flexible leasing options, and responsive on-site technical support.
Frequently Asked Questions (FAQ)
How do I convert scale 1:100 to 1:50?
To go from scale 1:100 to 1:50, you need to enlarge the document to 200%. You do this by dividing the current scale (100) by the desired scale (50) and multiplying by 100: (100 / 50) x 100 = 200%.
What scale do I get if I print A1 on A3?
A3 is linearly exactly 50% of an A1 format. This means the scale denominator doubles. If your original A1 plan was drawn at a scale of 1:100, this results in a scale of 1:200 after reduction to A3.
How big is 1 meter on a scale of 1:50?
At a scale of 1:50, every actual dimension is reduced 50 times on paper. 1 meter (or 100 centimeters) divided by 50 equals 2 centimeters. So 1 meter is 2 cm on the plan.
How do I calculate a distance on a building plan?
Measure the distance on the plan with a ruler in millimeters or centimeters, and multiply this by the scale denominator (for example, 100 for a 1:100 scale). Thus, 5 cm on a 1:100 plan equals (5 x 100) = 500 cm or 5 meters in reality.
Use this scale calculator
This scale calculator from Europlan may be freely used and shared as a tool for technical drawings and building plans. Do you want to refer to it from a course, manual, or website? Then link to this page.