About Diorama Fern

What it is

Diorama Fern is for scale modellers, model railway builders, wargamers, diorama makers and people who grow terrariums and bottle gardens. It converts real sizes to model sizes and back, prints scale rulers, resizes plans between scales, works out railway gradients, curve radii and helixes, and plans terrarium layers and plants. Lengths are in millimetres, centimetres and inches side by side, and volumes in litres and US quarts.

Where the numbers come from

Each page lists its sources. Model railway scales and gauges come from the standards bodies: the NMRA (S-3.2, RP-11 and RP-7.1) for North America and MOROP's NEM standards (NEM 010 and NEM 101) for Europe, and where the two disagree the pages say so. Kit and dollhouse scales are conventions and are labelled as such; figure scales in millimetres are approximate, because makers measure them differently. Terrarium layers follow UF/IFAS and Clemson extension guidance, and every plant on the picker links to its NC State Extension page. Anything we could not source is left out.

How it works

The calculators run entirely in your browser. Nothing you type is sent anywhere, there are no accounts, ads or cookies, and the pages keep working offline once loaded. The site uses Cloudflare Web Analytics, which counts page views without cookies or cross-site tracking and never receives what you type into the tools. The privacy page has the details.

Spotted a figure that looks wrong? Check it against the source linked on that page, which always wins.