Last updated August 2, 2026
A drawing scale is one number, and that number does four jobs. Get it right once at the start and the text, the dimensions, the hatching and the linetypes all come out at the size you meant. Get it wrong and every one of them is wrong together — which is why “my text is too small” is the most common thing a new drafter ever asks.
paper height × scale factor = model text height
The scale factor is just the number after the colon. A 1:100 drawing has a factor of 100. Everything below follows from that.
The recommended scales
The scales recommended for use with the metric system are:
- Actual size — 1:1
- Reduction — 1:2, 1:2.5, 1:5, 1:10
- Enlargement — 2:1, 5:1, 10:1
Decimal multiples of these base scales are also used: 1:100, 1:250, 20:1 and so on. That is where the long list in the chart below comes from — it is the same handful of base scales shifted by powers of ten.
Metric scale chart
Find the scale, read the factor, then read across to the height you want the text to be on the printed sheet. That last number is what you set the text height to in the model.
| Scale | Factor | 1.8 mm | 2.5 mm | 3.5 mm | 5 mm | 7 mm |
|---|---|---|---|---|---|---|
| 10:1 | 0.1 | 0.18 | 0.25 | 0.35 | 0.5 | 0.7 |
| 5:1 | 0.2 | 0.36 | 0.5 | 0.7 | 1 | 1.4 |
| 2:1 | 0.5 | 0.9 | 1.25 | 1.75 | 2.5 | 3.5 |
| 1:1 | 1 | 1.8 | 2.5 | 3.5 | 5 | 7 |
| 1:2 | 2 | 3.6 | 5 | 7 | 10 | 14 |
| 1:2.5 | 2.5 | 4.5 | 6.25 | 8.75 | 12.5 | 17.5 |
| 1:5 | 5 | 9 | 12.5 | 17.5 | 25 | 35 |
| 1:10 | 10 | 18 | 25 | 35 | 50 | 70 |
| 1:20 | 20 | 36 | 50 | 70 | 100 | 140 |
| 1:25 | 25 | 45 | 62.5 | 87.5 | 125 | 175 |
| 1:50 | 50 | 90 | 125 | 175 | 250 | 350 |
| 1:100 | 100 | 180 | 250 | 350 | 500 | 700 |
| 1:200 | 200 | 360 | 500 | 700 | 1000 | 1400 |
| 1:250 | 250 | 450 | 625 | 875 | 1250 | 1750 |
| 1:500 | 500 | 900 | 1250 | 1750 | 2500 | 3500 |
| 1:1000 | 1000 | 1800 | 2500 | 3500 | 5000 | 7000 |
| 1:1250 | 1250 | 2250 | 3125 | 4375 | 6250 | 8750 |
| 1:2500 | 2500 | 4500 | 6250 | 8750 | 12500 | 17500 |
Two things worth noticing. The enlargement rows run the other way — at 10:1 a note that prints 2.5 mm high is drawn 0.25 mm high in the model, because the drawing is ten times larger than the thing. And at 10:1 the whole column reads 0.18, 0.25, 0.35, 0.5, 0.7, which is the ISO pen width series exactly. Both series are defined by dividing by ten, so they land on the same numbers.
Imperial scale chart
An imperial scale is written as the length that stands for one foot, so the factor is 12 divided by that length. At 1/4” = 1′-0” a foot is drawn a quarter of an inch long, and 12 ÷ 0.25 = 48. Every factor below is worked out that way, which is why 1/8” text comes out at exactly 6”.
Architectural scales
| Scale | Factor | 3/32″ | 1/8″ | 3/16″ | 1/4″ |
|---|---|---|---|---|---|
| 3″ = 1′-0″ | 4 | 3/8″ | 1/2″ | 3/4″ | 1″ |
| 1 1/2″ = 1′-0″ | 8 | 3/4″ | 1″ | 1 1/2″ | 2″ |
| 1″ = 1′-0″ | 12 | 1 1/8″ | 1 1/2″ | 2 1/4″ | 3″ |
| 3/4″ = 1′-0″ | 16 | 1 1/2″ | 2″ | 3″ | 4″ |
| 1/2″ = 1′-0″ | 24 | 2 1/4″ | 3″ | 4 1/2″ | 6″ |
| 3/8″ = 1′-0″ | 32 | 3″ | 4″ | 6″ | 8″ |
| 1/4″ = 1′-0″ | 48 | 4 1/2″ | 6″ | 9″ | 1′ |
| 3/16″ = 1′-0″ | 64 | 6″ | 8″ | 1′ | 1′-4″ |
| 1/8″ = 1′-0″ | 96 | 9″ | 1′ | 1′-6″ | 2′ |
| 3/32″ = 1′-0″ | 128 | 1′ | 1′-4″ | 2′ | 2′-8″ |
| 1/16″ = 1′-0″ | 192 | 1′-6″ | 2′ | 3′ | 4′ |
| 1/32″ = 1′-0″ | 384 | 3′ | 4′ | 6′ | 8′ |
Civil and engineering scales
| Scale | Factor | 3/32″ | 1/8″ | 3/16″ | 1/4″ |
|---|---|---|---|---|---|
| 1″ = 10′ | 120 | 11 1/4″ | 1′-3″ | 1′-10 1/2″ | 2′-6″ |
| 1″ = 20′ | 240 | 1′-10 1/2″ | 2′-6″ | 3′-9″ | 5′ |
| 1″ = 30′ | 360 | 2′-9 3/4″ | 3′-9″ | 5′-7 1/2″ | 7′-6″ |
| 1″ = 40′ | 480 | 3′-9″ | 5′ | 7′-6″ | 10′ |
| 1″ = 50′ | 600 | 4′-8 1/4″ | 6′-3″ | 9′-4 1/2″ | 12′-6″ |
| 1″ = 60′ | 720 | 5′-7 1/2″ | 7′-6″ | 11′-3″ | 15′ |
| 1″ = 100′ | 1200 | 9′-4 1/2″ | 12′-6″ | 18′-9″ | 25′ |
| 1″ = 200′ | 2400 | 18′-9″ | 25′ | 37′-6″ | 50′ |
Where the factor goes in CAD
The same number goes into three settings, and there is a fourth that catches almost everybody.
| Setting | Value | Notes |
|---|---|---|
| Text height | paper height × factor | The chart above. 2.5 mm text at 1:100 is drawn 250 mm high. |
| DIMSCALE | the factor | Scales the whole dimension — text, arrows, extension line offsets, the lot. |
| Hatch scale | the factor | So the pattern prints at the spacing it was defined at. |
| LTSCALE | usually 1, not the factor | See below. This is the one that is wrong on most charts. |
The LTSCALE trap
Older references — and most scale charts still online — tell you to set LTSCALE to the scale factor. That was correct before AutoCAD 2008 and it is still correct if MSLTSCALE and PSLTSCALE are both 0.
Since AutoCAD 2008 both of those default to 1. MSLTSCALE at 1 scales linetypes on the Model tab by the annotation scale, and PSLTSCALE at 1 keeps linetype patterns consistent between viewports whatever scale each one is at. With those defaults LTSCALE stays at 1. Setting it to the factor as well scales the dashes twice, and you get a drawing where every hidden line looks continuous.
If your dashes are out by a factor of about 25, that is a different problem — it is the imperial linetype file loaded on a metric drawing. And if they look right in model space but wrong through a viewport, see PSLTSCALE.
Or let AutoCAD do it
An annotative object carries its paper height rather than its model height. Set the height you want on the sheet once, give each viewport its scale, and every multiplication in the charts above happens for you — including in a drawing where two details sit on the same sheet at different scales.
The charts are still what you need for anything that is not annotative: older drawings, drawings from other offices, blocks with hard-coded attribute heights, and anything drawn straight into paper space.
Indication of scale
The scale should normally be noted in the title block of a drawing. When more than one scale is used they should be shown close to the views they refer to, and the title block should read “scales as shown”.
If a drawing uses predominantly one scale, note that scale in the title block together with the wording “or as shown”.
A drawing that has been printed at anything other than its stated scale should be marked NTS, and no dimension should ever be scaled off it.
Printable scale chart
Download the drawing scale chart (PDF) — one A4 landscape sheet with all 36 scales, metric and imperial side by side, the factor for each and the model text height for every plotted height. Print it once and it answers the question for good.
There are matching printable charts for text heights and for sheet sizes.
References
- ISO 5455:1979, Technical drawings — Scales, for the recommended scale series. iso.org
- ISO 3098-0:1997, Technical product documentation — Lettering — Part 0: General requirements, for the plotted height series used in the columns above. iso.org
- Autodesk, How to manage linetype scale system variables (MSLTSCALE and PSLTSCALE) in AutoCAD, for the post-2008 defaults. autodesk.com
- Autodesk, LTSCALE and PSLTSCALE system variables in AutoCAD. autodesk.com
- Text heights in drawings — the height series in detail, with the pen width that belongs to each.
- Common metric structural scales — which scale suits which drawing.
- Understanding annotation scales in AutoCAD.
- Pen sizes and line types (metric).