Which putty should I use for plastic model kits?

For small gaps, liquid poly cement pressed into seams works well. For medium gaps, Tamiya Basic putty (polyester) or Mr Surfacer 500 are popular. For large gaps, Milliput or Green Stuff epoxy putties are better as they do not shrink. CA glue with accelerator is fast but hard to sand.

How do I estimate gap width on a kit?

Dry-fit the parts and look at the join under a bright light. Gaps under 0.3mm can often be closed with thin cement and pressure. Gaps of 0.3-1mm suit standard putty. Gaps over 1mm may need strip styrene backing before filling.

How much putty do I lose to sanding?

Typically 30-50% of the applied putty is sanded away during finishing. This calculator includes a waste factor to account for overfill and sanding. Apply slightly more than needed and sand back to the surface for the smoothest result.

ModelCalcs

Putty Usage Calculator — Gap Filling

Calculate modelling putty volume needed for gap filling based on seam length, width and depth.

Number of Seams

Seams or gaps that need filling

Average Seam Length

Average length of each seam

Average Gap Width

Width of the gap to fill

Average Gap Depth

Depth of the gap to fill

Putty TypeType of filler product

Kit ScaleModel scale for reference

How We Calculate This

Volume Calculation

Volume per seam = Length x Width x Depth

Total volume = Volume per seam x Number of seams

Total with waste = Total volume x Waste factor (accounts for overfill and sanding)

Weight = Volume x Putty density

Frequently Asked Questions

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Last updated: March 2026

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