ModelCalcs.uk
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.
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
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.
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.
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.
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.
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Calculate plaster, foam and texture materials for diorama groundwork.
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Last updated: February 2026
All calculations are estimates. Always verify quantities before purchasing materials.