How much ballast do I need for OO gauge track?

As a working figure, OO gauge single main-line track uses roughly 100ml of loose ballast per metre — about 150g by weight. This matches the well-known coffee-mug rule of thumb: a standard mug of ballast (~300ml) covers about 3 metres of OO single track with a moderate shoulder. So 6m of single OO track needs around 600ml (~900g). Double track and points need roughly double the width, and a wider shoulder multiplier adds more again.

What type of ballast should I use?

Use real crushed granite chippings in the correct grade for your scale. For OO gauge use fine grade (around 1mm); for N gauge use extra fine. Avoid coloured craft sand as it looks unrealistic. Limestone ballast is available for pre-grouping era layouts. UK ballast is sold by weight — typical bags are Javis 240g resealable, 670g, and 1kg granite chippings — so this calculator gives you a weight in grams and a 500g-bag count to make ordering easy.

How do I fix ballast in place?

Lay dry ballast, shape the shoulder with a soft brush, then wet it with a 50:50 mix of PVA glue and water plus a drop of washing-up liquid to break the surface tension. Apply the diluted solution with a pipette or fine spray. The "fixing solution" figure here is the total diluted mix you apply (about 0.4 × the ballast volume, enough to soak through the ~45% void space) — half of that volume is neat PVA. Allow 24 hours to dry fully before running trains.

How wide should the ballast shoulder be?

Main line ballast extends about one sleeper length beyond the track on each side with a gentle shoulder. Branch line ballast is narrower; yard and siding ballast is often minimal, barely covering the sleeper ends. This calculator drops the quantity for branch (×0.75) and yard (×0.6) profiles, and the Shoulder Width Multiplier lets you go wider (up to ×2) for a deep prototype shoulder or cork bed.

Ballast Quantity Calculator — Free Model Railway Tool

Ballast Quantity Calculator — Ballast for Model Railway Scenery

Calculate ballast volume, weight, PVA glue and bags needed for model railway track by scale and profile.

Track Length

Total run of track to ballast, in metres

Track TypeSingle, double, or points/turnout — sets the ballast width

ScaleYour modelling scale — sets width and depth (OO uses 40mm × 5mm)

Ballast ProfileMain (full), branch (×0.75) or yard/siding (×0.6)

How We Calculate This

This calculator estimates how much loose ballast you need from the track width at your chosen scale, the laying depth, the run length and a profile factor, with a fill factor that models ballast as a thin sloped shoulder rather than a solid block.

The formula

Volume = Track width × Depth × Length × Profile factor × 0.5 fill factor

The 0.5 fill factor reflects that real ballast is a shouldered layer with voids, not a full rectangular slab. It is calibrated to the coffee-mug rule (a ~300ml mug covers ~3m of OO single ≈ 100ml/m).

Weight = Volume × 1.5g/ml — the loose bulk density of crushed granite ballast (1.4–1.6 g/cm³).

Fixing solution = Volume × 0.4 — the total diluted mix needed to soak through the ~45% void space. It is a 50:50 PVA:water mix, so half of that volume is neat PVA. (The 50:50 is the mix ratio; the 0.4 is how much mix to make.)

Bags = Weight ÷ 500g, rounded up — UK ballast is sold by weight, not volume.

Frequently Asked Questions

Last updated: March 2026

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