🚿 Free Bathroom Calculator

Bathroom Renovation Calculator

Get a complete materials list for tile, grout, backer board, and paint — all in one estimate.

🚿 Bathroom Materials Estimator

📊 Materials Estimate

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How to Use This Calculator

  1. Enter the bathroom length and width in feet — measure the full room footprint at its widest points.
  2. Choose your wall tiling scope. Full walls gives the most complete look but costs the most material. Shower/tub area only is the most common renovation scope. Floor only is the most affordable option.
  3. If tiling shower/tub walls only, enter the height you want the tile to reach — typically 5 ft from the floor to the top of the tile field.
  4. Select your floor and wall tile sizes separately. Floor and wall tiles often differ — large-format floor tiles with subway wall tiles is a popular combination.
  5. Click Calculate to get a complete materials list including tiles, grout bags, backer board sheets, and paint gallons.

The Formula Explained

Floor tiles = (L × W × 1.15) ÷ tile sq ft  |  Grout bags = ceil((floor + wall sq ft) ÷ 50)  |  Backer board = ceil(wall sq ft ÷ 15)

All tile quantities include a 15% waste factor — the industry standard for cuts at walls, breakage, and pattern alignment. For diagonal layouts or complex herringbone patterns, add 20–25% instead. Grout coverage is approximately 1 bag per 50 square feet (actual coverage varies by tile size and joint width). Cement backer board comes in 3×5 sheets (15 sq ft each) and is required in all wet areas — never use standard drywall behind tile in a shower or tub surround. Paint is estimated at 350 sq ft per gallon for the remaining untiled wall area, with a standard door (20 sq ft) and window (10 sq ft) subtracted.

Tile & Materials Buying Guide

Frequently Asked Questions

Do I need cement backer board everywhere?
Only in wet areas — shower walls, tub surround, and the floor substrate in the tile area. Dry areas like accent walls or the wall behind a vanity that never gets splashed can use moisture-resistant drywall ("green board" or "purple board"), which is cheaper and easier to work with. Never use standard drywall in any area that will regularly get wet — it will swell, crumble, and cause tile failure within a few years.
What's the standard waste factor for tile?
10–15% for simple rectangular rooms with straight tile layouts. Use 15% for standard bathrooms, which is what this calculator applies. Add 20% for diagonal (45-degree) layouts, which waste more at the perimeter cuts. Add 20–25% for complex patterns like herringbone or basketweave. Always buy extra and keep the remainder — tiles from different production lots can vary slightly in shade and size, making future patch repairs a challenge if you run short.
Can I tile over existing tile?
Sometimes — if the existing tile is firmly bonded (no hollow spots), flat, and the added weight and thickness won't stress the floor structure or create a height difference at the door threshold. Check local building code, as some jurisdictions limit maximum tile layers. The biggest risk is that the added thickness (typically 3/8–1/2 inch per layer) can make toilet flanges and door thresholds problematic. When in doubt, remove the existing tile for a better, longer-lasting result.
How many coats of paint does a bathroom need?
Two coats minimum with a satin or semi-gloss finish specifically rated for high-humidity environments. Flat paint is porous — it absorbs moisture, is difficult to clean, and will show mold growth much faster than a washable finish. Semi-gloss is the traditional choice for bathrooms because it wipes clean easily and resists moisture best. Allow the first coat to dry fully (4–6 hours) before applying the second coat. In poorly ventilated bathrooms, consider an antimicrobial paint additive or a paint with built-in mildew resistance.
What size tile makes a small bathroom look bigger?
Larger tiles (12×12 or 18×18) with minimal grout lines create fewer visual breaks, making small bathrooms appear larger and more open. Light-colored large-format tiles are especially effective. Avoid very small mosaic tiles on the floor of a small bathroom — the many grout lines create a busy, chopped-up look that makes the space feel smaller. For walls, vertical subway tile (3×6 installed in a vertical stack bond pattern) draws the eye upward, making the ceiling feel higher.

💡 Pro Tip: Buy 15–20% extra tile and keep the leftovers. Tile lots change between production runs, so future patch repairs may not match if you run short.