You want to build a replica of your house. You know it is 30 feet wide. How many studs is that? You want the front door to be 7 feet tall. How many bricks? You want the porch railing to be 3 feet high. How many plates?
If you are building at minifigure scale, the horizontal answer is simple — 1 stud equals roughly 1 foot. But the vertical math is different because LEGO bricks are not cubes. A brick is wider than it is tall. A plate is exactly one-third the height of a brick. And the conversion changes entirely if you are working at Speed Champions scale, Technic scale, or microscale.
Most builders solve this with a pencil, a calculator app, and a lot of rounding. Some keep a spreadsheet. Some memorize the key ratios and eyeball everything else. All of these approaches work, but they are slow, error-prone, and interrupt the creative flow of designing a MOC.
That is why I built The Earl's Scale Calculator — a free, instant tool that lives right on the Scale Guides page. Enter a real-world measurement, pick your scale, and get every number you need in one glance.
The calculator takes three inputs:
- A real-world measurement — the actual dimension of the thing you want to build. The width of a building. The height of a doorway. The length of a car. Whatever you are trying to replicate in brick.
- A unit — feet, inches, meters, or centimeters. Use whatever unit your reference material is in. No need to convert beforehand.
- A scale — pick from seven built-in LEGO scales, or enter a custom ratio for non-standard builds.
From those three inputs, the calculator instantly returns four results:
There is also a fifth output that most calculators do not provide: the Optimal Brick + Plate Combo. Because LEGO dimensions are discrete — you cannot use half a plate — the exact height you need almost never lands perfectly on a whole number of bricks. The calculator finds the combination of bricks and plates that gets closest to the mathematically correct height, and tells you the error in millimeters and percentage. This is the difference between a wall that is "close enough" and a wall that is engineered.
The calculator ships with seven preset scales that cover the vast majority of LEGO building:
| Scale | Common Name | 1 Foot = | Best For |
|---|---|---|---|
| 1:38 | Minifig / City | 1 stud | City layouts, modular buildings, train scenes, most MOCs |
| 1:45 | Small Minifig | 0.85 studs | Slightly smaller builds, some official LEGO City sets |
| 1:30 | 8-Wide Speed Champions | 1.27 studs | Speed Champions display scenes, 8-wide car dioramas |
| 1:28 | Large Speed Champions | 1.36 studs | Larger Speed Champions builds, some custom car MOCs |
| 1:10 | Technic | 3.81 studs | Technic vehicles, large display models |
| 1:8 | Technic Flagship | 4.76 studs | Technic flagship sets like the Porsche GT3 RS, Bugatti Chiron |
| 1:200 | Microscale | 0.19 studs | Skylines, cityscapes, Architecture-style builds |
If your project uses a non-standard scale — say 1:50 for a large architectural model or 1:150 for a model railway scene — select Custom Scale from the dropdown and type your ratio. The math works the same way regardless of the number.
One of the most useful features is the collapsible comparison table below the main results. Click "Compare All Scales at Once" and the calculator shows your measurement converted across all seven scales simultaneously.
This is invaluable when you are in the planning phase and have not committed to a scale yet. Type in the key dimension of your subject — the width of the building, the length of the vehicle, the height of the landmark — and instantly see how large the finished model would be at every scale. If your 100-foot building turns out to be 31 inches at minifig scale but only 6 inches at microscale, that comparison helps you decide which scale fits your display space and budget.
The table also highlights the currently selected scale in amber, so you can quickly scan across the row and see how your chosen scale compares to the alternatives.
Under the hood, the calculator uses three fundamental LEGO dimensions that every serious builder should know:
- 1 stud = 8mm (center-to-center horizontal spacing)
- 1 brick height = 9.6mm (the body of the brick without the stud on top)
- 1 plate height = 3.2mm (exactly one-third of a brick)
The calculation is straightforward. Take the real-world measurement in millimeters, divide by the scale ratio to get the model size in millimeters, then divide by the element dimension (8mm for studs, 9.6mm for bricks, 3.2mm for plates) to get the count. The optimal combo algorithm tests every possible combination of bricks and plates up to the target height and returns the one with the smallest error.
These are the same numbers LEGO designers use. The same numbers the IMS Pagoda scale math article derives from first principles. The calculator just does it instantly so you can focus on building instead of arithmetic.
Scale is the invisible engineering that makes a MOC look right. The calculator handles the math. You handle the art.
Planning a Building MOC
You have floor plans or photos of a real building. Measure the facade width, the floor-to-floor height, the window openings. Plug each dimension into the calculator at 1:38 and you have your stud counts before you touch a single brick. This is how I planned every wall of the IMS Pagoda — real-world reference measurements converted to studs, validated against the minifigure standing next to the model.
Checking Vehicle Scale Compatibility
You want to park a Speed Champions car next to a building. But will it look right? Enter the real car's width (about 6 feet for a sports car) and check both 1:38 and 1:30. If the stud counts are dramatically different, the scales will clash in your display. This is exactly the 6-wide vs. 8-wide problem that trips up so many builders.
Designing in Stud.io
Before you start placing bricks in Stud.io, use the calculator to establish your key dimensions. How wide is the building footprint in studs? How tall is each floor in bricks and plates? Having these numbers written down before you open the software means less trial-and-error and fewer teardowns. The Stud.io Modular Buildings tutorial walks through this exact workflow.
Settling Scale Debates
Someone in your LUG says a door should be 5 bricks tall at minifig scale. Someone else says 4. Enter 6.5 feet (a standard residential door height) at 1:38 and the calculator settles it: the answer is 5.5 bricks, which means 5 bricks plus 1 plate is close, or 4 bricks plus 5 plates for precision. Math beats opinion every time.
Microscale Feasibility Checks
At microscale, the numbers get small fast. A 200-foot building at 1:200 is only 19 studs wide. A car is less than one stud. The calculator shows you immediately whether your subject can even be represented at your chosen microscale — before you waste time trying to build something that the resolution of LEGO simply cannot capture.
The Earl's Scale Calculator is free, instant, and requires no account or download. It lives on the Scale Guides page alongside the complete guide to every LEGO scale, the cross-reference table comparing LEGO to diecast model scales, and tips for choosing the right scale for your MOC.
Bookmark it. Use it every time you start a new build. Share it with your LUG. The math should never be the hard part — the building should be.
For the full theory behind LEGO scale — why minifig scale is 1:38, how to choose between 6-wide and 8-wide vehicles, and the vertical scaling tricks that make buildings look proportionally correct — read the complete Scale Guides article. And for a real-world case study of scale calculations applied to a complex MOC, see the IMS Pagoda Scale Math breakdown.