Glass Block Calculator

How it works

columns = round(width ÷ module) · rows = round(height ÷ module) · blocks = columns × rows · mortar ≈ blocks × 2 × module × joint × block depth × 1.25 · reinforcement = ⌊(rows − 1) ÷ 2⌋ × panel width

Glass blocks cannot be cut, so the panel is planned in whole modules: the block plus one joint, 20 cm for 19 cm blocks with 1 cm joints and 8 in for 7¾ in blocks with ¼ in joints. The opening is rounded to the nearest whole number of blocks and the finished panel size shows how much to adjust it. Each block needs mortar along one bed joint and one head joint across its full depth; 25% is added for waste. Manufacturers call for ladder-type panel reinforcement in every second horizontal joint (about every 40 cm or 16 in), an expansion strip at the jambs and head so the panel can move, and plastic spacers at the joint intersections when laying.

Worked example

A 2.0 × 1.6 m opening with 19 × 19 cm blocks (20 cm module): 2.0 ÷ 0.2 = 10 columns and 1.6 ÷ 0.2 = 8 rows, so 80 glass blocks for a 2.00 × 1.60 m panel. Mortar ≈ 80 × 2 × 0.2 × 0.01 × 0.08 × 1.25 = 32.0 L wet (about 61 kg of dry mix); 99 spacers; reinforcement in 3 joints = 6.0 m; expansion strip 5.2 m.

Sources: Pittsburgh Corning — Glass block installation guide · ACI 530/TMS 402 Building Code Requirements for Masonry Structures — glass unit masonry

Frequently asked questions