1508
Mortar chart
Put your area, coverage per bag and waste allowance in: 400 sq ft at 10% waste needs 7.33 bags exact, order 8.
★ CONSTRUCTION · MORTAR · COVERAGE CHART
Mortar Coverage Chart: 8 Bags for 400 Sq Ft at 10% Waste
On the defaults — 400 square feet at 10% waste with 60 square feet per bag coverage — you need 440.00 square feet of mortar, 7.33 bags exact, so order 8 bags. This is the MORTAR version — area times waste divided by coverage, with a lookup table for every common area and coverage — the paint-chart page is the PAINT version — the same divide-and-round-up model counted in topcoat gallons; the primer-chart page is the PRIMER version — the same model counted in primer gallons; the drywall-chart page is the SHEET version — the same model counted in sheets; and the stain-chart page is the STAIN version — the same model counted in stain gallons.
What does 7.33 bags, order 8, mean?
It means that 400 square feet of surface, with a 10% waste allowance, need 440.00 square feet of mortar, and at 60 square feet per bag that is 7.33 bags — seven full bags plus a third of an eighth — and because mortar is sold by the bag, you order 8. The rounding is the whole story in miniature: a partial bag cannot be bought in the quantity needed, so any fraction, however small, becomes a whole bag. The part people get wrong is rounding to the nearest bag instead of up: 7.33 rounded to the nearest is 7 here, and 7 bags cover only 420 square feet, leaving 20.00 square feet without mortar. The other part people get wrong is the exact fit: 440 square feet of coverage need exactly 1.00 bag at 440 square feet per bag, and order exactly 1, because the rounding is up to the next whole bag, not up plus one — an exact fit needs no spare bag from the rounding, though a spare for touch-ups is a separate decision.
Three things to check before you trust the number
Is 60 square feet per bag right for your mortar and trowel? Sixty square feet per 50-pound bag is the figure this page uses, and it matches the published range for a 1/4-by-3/8-inch square-notch trowel, roughly 60 to 70 square feet per bag. A larger notch lays a thicker bed and covers less: a 1/2-inch notch covers roughly 35 to 50 square feet per bag, so the same 400 square feet at 40 square feet per bag would need 11 bags, not 8. Enter the coverage your mortar maker publishes for your trowel size, rather than trusting the default for a thick-bed job.
Did you measure every surface? The area entered here must be the total of all surfaces, not the largest single wall or floor: a room with 400 square feet of floor plus splashbacks, niches and returns has more than 400 square feet to cover. The 200-square-foot branch needs 3.67 bags, order 4, against the 7.33-bag headline, so missing one section understates the order by whole bags on a bigger job. Measure every surface, add them before dividing, and do not subtract small gaps unless your mortar maker says to.
Are you counting waste, or a second layer? This page adds 10% for waste — spillage, cuts, mixing loss and touch-ups — and that is not a second layer. A second layer doubles the area first: 400 square feet twice-covered is 800 square feet before waste, which is 880.00 square feet with waste and 14.67 bags, order 15. Treating a second layer as waste, or waste as a second layer, misstates the order by whole bags either way, so decide the layers first and let the waste percentage stay at waste.
Worked example
On the defaults: 400 square feet, 60 square feet per bag, 10% waste.
- Needed area: 400 × 1.10 is 440.00 square feet.
- Exact bags: 440.00 ÷ 60 is 7.33 bags.
- Order: 7.33 rounded up is 8 bags — the 0.33 is a third of a bag that must be bought whole.
- Check: 8 bags cover 480 square feet, which is more than the 440.00 needed; 7 bags cover only 420, which is not enough.
And the other way: the area behind 7.33 bags is 400 square feet, the coverage behind 7.33 bags is 60 square feet per bag, and the waste behind 7.33 bags is 10%. A job at 440 square feet per bag orders exactly 1 bag, and the 800-square-foot, 40-square-feet-per-bag lookup row lands exactly on 22.00 bags, order 22.
Every branch, checked
- 200 square feet, 60 square feet per bag, 10% waste: 200 square feet, 60 square feet per bag, 10% waste: 3.67 bags exact — order 4 bags.
- 800 square feet, 60 square feet per bag, 10% waste: 800 square feet, 60 square feet per bag, 10% waste: 14.67 bags exact — order 15 bags.
- 400 square feet, 80 square feet per bag, 10% waste: 400 square feet, 80 square feet per bag, 10% waste: 5.50 bags exact — order 6 bags.
- 400 square feet, 60 square feet per bag, 20% waste: 400 square feet, 60 square feet per bag, 20% waste: 8.00 bags exact — order 8 bags.
The reverses, worked backwards
- Area behind 7.33 bags: 400 sq ft — at 400 sq ft the figures are 7.33 bags exact — order 8 bags.; at the lower neighbor the figures are 6.42 bags exact — order 7 bags.; at the upper neighbor the figures are 8.25 bags exact — order 9 bags..
- Coverage behind 7.33 bags: 60 sq ft per bag — at 60 sq ft per bag the figures are 7.33 bags exact — order 8 bags.; at the lower neighbor the figures are 8.80 bags exact — order 9 bags.; at the upper neighbor the figures are 6.29 bags exact — order 7 bags..
- Waste behind 7.33 bags: 10% waste — at 10% waste the figures are 7.33 bags exact — order 8 bags.; at the lower neighbor the figures are 7.00 bags exact — order 7 bags.; at the upper neighbor the figures are 7.67 bags exact — order 8 bags..
What the defaults assume
The defaults are 400 square feet, 60 square feet per bag and 10% waste, so the headline is one layer of a bagged mortar over a medium room, at the coverage of a 1/4-by-3/8-inch square-notch trowel. The model is a multiplication, a division and a ceiling: needed area is area times one plus the waste percentage, exact bags are needed area divided by coverage per bag, and the order rounds exact bags up to the next whole bag, with a 1e-12 epsilon so an exact whole number orders exactly that many. Bag sizes differ — the 60-square-feet figure is for a standard 50-pound bag, and a smaller bag covers proportionally less, so enter the coverage for the bag you will actually buy. The area reverse is checked at 50 square feet either side, because 50 square feet at 10% waste is 55 square feet, about 0.92 bags; the coverage reverse is checked at 10 square feet either side, because 440.00 over 50 is 8.80 bags and over 70 is 6.29; the waste reverse is checked at 5% either side, because 5% of 400 is 20 square feet, about 0.33 bags. The model does not include second layers, mortar type differences beyond the coverage figure, substrate absorption beyond the waste allowance, or tools — count those separately.
Lookup table: bags by area and coverage
Each row already includes the 10% waste allowance: needed area is the area times 1.10, exact bags are needed area divided by the coverage in that row, and the order column rounds up. A row that lands exactly on a whole number orders exactly that many — no extra bag is added for an exact fit. For a different trowel, enter your own coverage in the calculator above: a larger notch covers fewer feet per bag, so the order rises.
| Area | Coverage per bag | Needed area | Exact bags | Order |
|---|---|---|---|---|
| 100 sq ft | 40 sq ft per bag | 110.00 sq ft | 2.75 | 3 bags |
| 100 sq ft | 60 sq ft per bag | 110.00 sq ft | 1.83 | 2 bags |
| 100 sq ft | 80 sq ft per bag | 110.00 sq ft | 1.38 | 2 bags |
| 100 sq ft | 100 sq ft per bag | 110.00 sq ft | 1.10 | 2 bags |
| 200 sq ft | 40 sq ft per bag | 220.00 sq ft | 5.50 | 6 bags |
| 200 sq ft | 60 sq ft per bag | 220.00 sq ft | 3.67 | 4 bags |
| 200 sq ft | 80 sq ft per bag | 220.00 sq ft | 2.75 | 3 bags |
| 200 sq ft | 100 sq ft per bag | 220.00 sq ft | 2.20 | 3 bags |
| 400 sq ft | 40 sq ft per bag | 440.00 sq ft | 11.00 | 11 bags |
| 400 sq ft | 60 sq ft per bag | 440.00 sq ft | 7.33 | 8 bags |
| 400 sq ft | 80 sq ft per bag | 440.00 sq ft | 5.50 | 6 bags |
| 400 sq ft | 100 sq ft per bag | 440.00 sq ft | 4.40 | 5 bags |
| 800 sq ft | 40 sq ft per bag | 880.00 sq ft | 22.00 | 22 bags |
| 800 sq ft | 60 sq ft per bag | 880.00 sq ft | 14.67 | 15 bags |
| 800 sq ft | 80 sq ft per bag | 880.00 sq ft | 11.00 | 11 bags |
| 800 sq ft | 100 sq ft per bag | 880.00 sq ft | 8.80 | 9 bags |
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Needed area | area × (1 + waste ÷ 100) | 440.00 sq ft — 400 × 1.10. |
| Exact bags | needed area ÷ coverage per bag | 7.33 bags — 440.00 ÷ 60. |
| Order | exact bags rounded up | 8 bags — 7.33 rounds up. |
| Area behind a target exact figure | exact bags × coverage per bag ÷ (1 + waste ÷ 100) | 400 sq ft — 7.33 × 60 ÷ 1.10. |
| Coverage behind a target exact figure | needed area ÷ exact bags | 60 sq ft per bag — 440.00 ÷ 7.33. |
| Bags covered by the order | order × coverage per bag | 480 sq ft — 8 × 60, more than the 440.00 needed. |
| Square feet short on one fewer bag | needed area − (order − 1) × coverage per bag | 20.00 sq ft — 440.00 − 7 × 60, which is why rounding down fails. |
| 200 square feet, 60 square feet per bag, 10% waste | same model | 3.67 bags exact — order 4 bags. |
| 800 square feet, 60 square feet per bag, 10% waste | same model | 14.67 bags exact — order 15 bags. |
| 400 square feet, 80 square feet per bag, 10% waste | same model | 5.50 bags exact — order 6 bags. |
| 400 square feet, 60 square feet per bag, 20% waste | same model | 8.00 bags exact — order 8 bags. |
| Area behind 7.33 bags | reverse | 400 sq ft: 7.33 bags exact — order 8 bags. |
| Coverage behind 7.33 bags | reverse | 60 sq ft per bag: 7.33 bags exact — order 8 bags. |
| Waste behind 7.33 bags | reverse | 10% waste: 7.33 bags exact — order 8 bags. |
| 0 square feet | same model | 0.00 bags exact — order 0 bags. |
| Negative area | same model | Area — 0 or more. |
| Zero coverage | same model | Coverage — more than 0. |
| 440 square feet per bag | same model | 1.00 bags exact — order 1 bags. |
Who uses this
- A DIYer tiling a room — 400 square feet at 10% waste is 8 bags, with the lookup table covering every other area and coverage without re-measuring.
- A tiler ordering for a job — the branches show how the order moves with area, coverage and waste, so a larger trowel notch is repriced before ordering.
- A homeowner comparing mortars — the 80-square-feet branch shows what a higher-coverage product really saves in bags, before the job starts.
- An estimator checking a quote — the reverses recover the area, coverage or waste behind any quoted bag count, which checks a quote without re-measuring the job.
Accuracy & limitations
Figures are the model’s own arithmetic on the numbers you type, computed from unrounded values and displayed rounded HALF_UP to 2dp, with orders rounded up using a 1e-12 epsilon so exact fits are not over-ordered. The main limitation is the coverage figure, not the arithmetic: published mortar coverage varies with product and trowel — roughly 60 to 70 square feet per 50-pound bag at a 1/4-by-3/8-inch square notch, and roughly 35 to 50 at a 1/2-inch notch — so check your product and enter your own figure when your trowel differs. This page is a calculation tool, not trade advice — follow the mortar maker’s instructions for mixing, application and curing.
Cite this calculator
400 square feet at 10% waste with 60 square feet per bag coverage needs 440.00 square feet, 7.33 bags exact: order 8 bags. Source: Bright Side Kit, https://brightoolbox.com/mortar-chart/, accessed 29 October 2026.
Frequently asked questions
How many square feet does one bag of mortar cover?
This page uses 60 square feet per 50-pound bag, which matches the published range for a 1/4-by-3/8-inch square-notch trowel, roughly 60 to 70 square feet. A larger notch lays a thicker bed and covers less — a 1/2-inch notch covers roughly 35 to 50 square feet per bag — so enter the coverage your product publishes for your trowel size: the calculator divides by whatever you enter, so the answer stays honest for your job.
Is this chart for mortar or thinset?
Both, as long as the coverage figure matches the product: thinset is the modern bagged mortar used for setting tile, and this page does not care about the name on the bag — it divides your area by your coverage figure. A thinset at 60 square feet per bag and a thick-bed mortar at 40 behave the same in the arithmetic and differently in the bag count, which is why the coverage figure, not the product name, decides the order.
Why add 10% waste?
Because mortar is lost to spillage, cuts, mixing and touch-ups: the 10% allowance covers the mortar that never ends up as a finished bed. Without it, a job that computes to exactly 7.00 bags would run dry on the last stretch of wall, and the waste percentage is what keeps the order honest for real application.
Why round up instead of to the nearest bag?
Because a partial bag cannot be bought in the quantity needed, and rounding down leaves surface uncovered: 7.33 bags rounded to the nearest is 7, and 7 bags cover only 420 of the 440.00 square feet needed. Rounding up guarantees the whole area is covered; the extra fraction is the price of buying whole bags.
What if the exact figure is already a whole number?
Then you order exactly that many: a job at 440 square feet per bag needs exactly 1.00 bag and orders 1, not 2, and the epsilon in the rounding protects exact fits, so a job that lands on a whole number is not charged an extra bag for nothing.
Does the waste allowance cover a second layer?
No: waste and layers are different things. Waste is the extra 10% for spillage, cuts and touch-ups on one layer; a second layer doubles the area first, so 400 square feet twice-covered is 800 square feet before waste, which is 880.00 square feet with waste and 14.67 bags, order 15. Decide the layers first, then let waste stay at waste.