How much border should I leave around my subject?

There is no fixed rule — base sizing is a compositional judgement (rule of thirds, breathing room). As a practical guide, a vehicle works well with about 25% extra per side (the 1.5× multiplier adds 50% across each axis, split into two end/side gaps). Figure groups benefit from more context (1.8× ≈ 40% per side) while a tight vignette can sit on 1.3× ≈ 15% per side. The calculator picks a sensible multiplier from your subject type, which you can override.

What base materials are best for dioramas?

MDF and plywood (3-6mm thick) are the most popular choices. MDF is flat and easy to cut but can warp if sealed badly. Plywood is stronger but heavier. Picture frames, wooden plaques and commercial diorama bases also work well.

Should the base be rectangular or can I use other shapes?

Rectangular and square bases are the most common and easiest to frame. Oval and circular bases work well for vignettes. Irregular shapes can add visual interest but are harder to display and transport.

Do I enter the model dimensions or the real-world dimensions?

Enter the model dimensions in millimetres. Measure your built model (or check the kit box for approximate finished dimensions). The calculator works from the model size to determine the base needed.

ModelCalcs

Base Size Calculator — Diorama Base Dimensions

Calculate the right diorama base dimensions from your built model's size. Accounts for border space and scene composition.

Subject TypeSets the default border multiplier: tanks/vehicles 1.5×, aircraft 1.4×, building 1.6×, figure group 1.8×, vignette 1.3×, landscape 1.2×

Model Length

Longest footprint dimension of your built model in mm (measure the finished kit, not the box)

Model Width

Footprint width across your built model in mm (include splayed tracks, wings or stowage)

Add scenic border

On: applies the subject multiplier for terrain and groundwork. Off: just minimal clearance around the model

How We Calculate This

The calculator takes your model dimensions and applies a border multiplier based on the subject type.

Formula

Base dimension = Model dimension × Border multiplier (applied to length and width separately)
Vehicle scenes use 1.5×, figure groups use 1.8×, vignettes use 1.3×
End gap (length axis) = (base length − model length) ÷ 2; side gap (width axis) = (base width − model width) ÷ 2 — these differ whenever the model is not square

These multipliers are a practical rule of thumb, not a fixed standard — diorama base sizing is ultimately a compositional judgement (rule of thirds, breathing room around the focal point). The border gives the subject room and prevents the scene feeling cramped. Treat the result as a starting point and adjust to suit your composition.

Frequently Asked Questions

Related Calculators

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Figure Placement Calculator

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.