Solve backwards
How much block wall will my block filler cover?
- 5 galThe example worked below
- Block Filler Coverage CalculatorEvery figure is its own
You have
How much block filler?
That is 5 gal(18.9 L). Worked by the Block Filler Coverage Calculator at the settings below.
The settings it uses
- Data Sheet Spread Rate
- 350 ft²/gal
- Block Texture Class
- Medium texture — ordinary lightweight block
- Waste Allowance (%)
- 10
What it will do
636 sq ft of block face
59.1 m²
One block wall. Enough for a block wall 79.5 ft long and 8 ft high.
Or several. Less than one block wall of the size the Block Filler Coverage Calculator opens on (a block wall 121 ft long and 8 ft high).
Check it forwards
- Net Wall Area
- 636 sq ft
- It asks for
- 5 gal
- You have
- 5 gal
The Block Filler Coverage Calculator asks for 5 gal at that size.
If you had more, or less
Around your amount
Each worked by the Block Filler Coverage Calculator at the same settings.
Half
2.5 gal
318 sq ft
a block wall 39.8 ft long and 8 ft high
Yours
5 gal
636 sq ft
a block wall 79.5 ft long and 8 ft high
Half as much again
7.5 gal
955 sq ft
a block wall 119 ft long and 8 ft high
Double
10 gal
1,273 sq ft
a block wall 159 ft long and 8 ft high
Common amounts
What each amount of block filler covers
The sizes it is usually sold in, each worked by the Block Filler Coverage Calculator at the settings above.
| You have | It covers | As one block wall | Average block walls |
|---|---|---|---|
| 1 gal(3.8 L) | 127 sq ft(11.8 m²) | a block wall 15.9 ft long and 8 ft high | under 1 |
| 5 gal(18.9 L) | 636 sq ft(59.1 m²) | a block wall 79.5 ft long and 8 ft high | under 1 |
| 10 gal(37.9 L) | 1,273 sq ft(118 m²) | a block wall 159 ft long and 8 ft high | 1 |
The pail's rate is for a smooth surface
Manufacturers publish a theoretical spread rate at a stated film thickness on a non-absorbent surface. The calculator divides it by a multiplier for how open the block face is — two and a half times at its medium class — so the filler here covers far less than the data sheet's number suggests.
Rub a dry hand over the wall
A face that leaves grit on your palm and shows open pinholes under a raking light is the open class; a dense architectural unit with a closed face is the light one. Where you cannot decide between two classes, price the coarser — running short halfway along a wall costs more than a leftover pail.
Ten per cent never reaches the wall
The calculator carries ten per cent for roller loading, spillage and cut-in touch-up, because a heavily loaded roller sleeve holds a surprising amount of thick filler. That allowance comes off what you have, so the wall here is shorter than the pail divided by the rate. Spraying loses more again to overspray and hose fill.
How the answer is worked
Nothing here is a second formula. The Block Filler Coverage Calculator runs forwards — a size in, a quantity out — and this page grows its own starting block wall in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.
Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.
Block Filler Coverage Calculator
runs it forwardsWork out how much block filler an open-textured masonry wall drinks on the first coat, against the data sheet's smooth-substrate rate.
Work out what to buy insteadSolve backwards
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Fence stain, worked by the Wood Fence Stain Calculator.
Solve backwards
Start from what is already in the yard
Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.
The calculator's own figures
Nothing is estimated twice: the page runs the same calculator you would order with.
The largest size that fits
Where a calculator rounds up to whole containers, the answer stops before the next one.
Both unit systems
Gallons and litres, square feet and square metres, side by side.
Frequently asked questions
- How much block face does 5 gal of block filler cover?
- At the Block Filler Coverage Calculator's own settings, 636 sq ft (59.1 m²) — a block wall 79.5 ft long and 8 ft high. Every figure follows the settings, which you can change in the calculator.
- How much block face does 20 L of block filler cover?
- At the Block Filler Coverage Calculator's own settings, 62.5 m² (673 sq ft) — a block wall 26.1 m long and 2.4 m high. Every figure follows the settings, which you can change in the calculator.
- How many square feet does a 5-gallon pail of block filler cover?
- Far less than its label suggests on real block. A data sheet might quote about 8.6 m² per litre (350 square feet per gallon) on a smooth surface, but a medium-textured block face takes two and a half times as much, and ten per cent more goes to the roller and spillage. The table above works it through.
- Do I need block filler before painting concrete block?
- On bare block that will be painted, generally yes — the filler closes the pinholes and open texture so the finish coats sit on a closed surface and run near their own rated coverage. It is not applied over previously coated smooth work.
- Why does block filler need a second pass sometimes?
- An unusually open wall can still show pinholes after the first coat. The calculator covers the first coat only; a second fill pass, patching and joint pointing are separate quantities, and the finish coats that follow go over a filled surface at close to their own rate.