Thinset Calculator

Estimate how many bags of thinset mortar you need based on tile size and trowel notch.

Use decimals when needed. This estimate updates live and is safe to tweak before you buy materials.

Estimated thinset

Thinset Buying Guide

This guide helps you turn your thinset calculator result into a cleaner purchase plan. Use it when you want fewer return trips, better waste assumptions, and a more realistic cart.

Step 1: Know your trowel notch size

Large 12x24 tiles require a deep 1/2-inch notched trowel, which consumes massive amounts of thinset. Small subway tiles use a 3/16-inch trowel and stretch the bag much further.

Step 2: Avoid pre-mixed buckets for floors

Pre-mixed 'mastic' in a bucket relies on air to dry. If you use it under large floor tiles, the center will never cure. Always buy dry bags of Portland cement thinset for floors.

Step 3: Check your waterproofing membrane

Systems like Schluter Kerdi often require unmodified thinset so it can cure properly between two impervious layers. Read the membrane manufacturer's instructions carefully.

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Commonly paired tools and accessories

These are the practical extras people often forget until the last minute, especially when turning a rough estimate into a real purchase list.

Modified Thinset Mortarvia Amazon.comWhy this helps: Common add-on that reduces last-minute store runs once the estimate is final.

Square Notch Trowelvia Amazon.comWhy this helps: Common add-on that reduces last-minute store runs once the estimate is final.

Disclosure: these may be affiliate links.

Thinset cost planning rule of thumb

Budget for the bags of thinset, a specialized mixing paddle for your drill, a few 5-gallon buckets, and the specific notched trowel required for your tile size.