When you start repairing, you will inevitably face the problem of how to correctly calculate the required amount of materials, in particular, wallpapers. Do you repair yourself, or do you need help from specialists? It's better to check how many rolls of wallpaper you need for each room.
How to calculate the quantity correctly
Buy the necessary materials will need a small margin, so that there is no need to run around the shops for the missing material. Moreover, wallpapers from different parties may differ in shades of colors, which will be noticeable in the pasted canvas.
Superfluous rolls, too, almost always do not find use, in addition, modern quality wallpapers are also not cheap. Throw a lot of money, so that the extra pair of rolls are then collected in the pantry is also not interesting.
Experts advise:
 To take advantage of the services of an experienced masterbuilder;
 Use the wallpaper calculator;
 Count the amount of material on the old wallpaper.
For an experienced master, counting the number of wallpapers will not cause difficulties. But if you are new to the paper wallpaper, you can use the services of a special construction calculator. Their developers propose to enter data on the size of the room and the width of the proposed wallpaper, and you will be given the result by the number of rolls.
We believe at our own peril and risk
If you decide to use the calculator, do not be lazy to read reviews about the results of calculating this calculator, but it will be better to calculate the number of rolls of wallpaper using several different calculators and compare the results.
It will be more correct to calculate on such a calculator, in the conditions of which the data on the number and area of windows and doors in the room being pasted, as well as the sizes of the rolls that you are going to use are laid. In different rooms of the same perimeter, there can be one window and one door, and maybe several, and three, and five. Calculating the size of the surface to be glued, the area of windows and doors will need to be subtracted from the total area of the room. Therefore, the error in the calculation, which the calculator gives, will be the less, the more parameters are included in the algorithm of its operation.
What is a construction calculator
On the other hand, there is nothing complicated in how to correctly calculate the number of rolls of wallpaper, without using a special construction calculator. To do this, you need to measure the perimeter of your room. If the room has a standard rectangular shape, you can measure two adjacent walls, add their size and multiply by two. This will be the perimeter of the room. If the room has a nonstandard form (in individual houses or as a result of replanning, or for some other reason), and if the room has ledges, niches or other nonstandard elements, you will need to measure the length of each straight segment of the wall using a tape measure and add up all the indicators.
It happens that because of the economy some parts of the walls are not supposed to be wallpapered. For example, if you have in your room are massive closets or a furniture wall, which you can not put in another way. If the rearrangement or replacement of furniture is not done, then the size of the wall behind the furniture will need to be subtracted from the calculations.
Specificity of material calculation
This determines the correctness of the calculation of the required number of materials. Then it is recommended to calculate how many whole canvas wallpapers are obtained from one roll. To do this, you need to measure the height of the wall to the ceiling or to the level on the wall to which you plan to paste the wallpaper. If you purchased or plan to purchase wallpaper without a picture, then do not need to make a correction for the alignment of the picture. In this case, it is necessary to divide the length of the roll into the length of one panel, which you determined when measuring the height of the wall to the ceiling, and calculate how many sheets of rolls will be produced.
Calculation examples
At ceiling heights up to 2.5 meters from one standard 10meter roll, four whole cloths are obtained (if there is no need to combine the pattern). If you buy a wallpaper that requires matching the canvases in the picture, you will need to make a correction for the alignment of the picture, the calculation for such wallpapers, see below in the text.
If the length of your panel (ceiling height) is more than 2.5 m, there will be only three whole panels, but from each roll you will get a large residue, almost in a panel that can be used, pasting doorways and space under and above window openings. In this case, perimeter of the room can be subtracted from the perimeter of doors and windows, and calculate only how much long cloths are required. The resulting perimeter of the walls is divided by the width of the roll, so you can count the number of long panels required for gluing the walls. Then the necessary number of panels per room multiplied by the resulting number of whole canvases from one roll, the result will be equal to the required number of rolls.
For example, your room has a perimeter of 25 m, a roll width of 0.5 m. The total number of panels for gluing such a room is 25: 0.5 = 50. At a ceiling height of up to 2.5 m, 4 webs are produced from a roll, the number of rolls 50: 4 = 12.5 is rounded to 13.
If you get a fractional value when counting, rounding is necessarily done in a larger direction. Do not forget in the calculations that all quantities must be in the same units of measurement. If you take the perimeter of the room in meters, then the width of the wallpaper roll is also used in meters, and do not forget to translate the remaining figures into meters. Otherwise, you will not get a reliable result, how much material you need.
Wallpaper without a pronounced pattern is easy to glue. Difficulties arise if the material has a large pattern, floral ornament or geometric pattern. In this case, you have to take into account the displacement of the pattern on the canvases in order to correctly combine adjacent strips.
Usually, the marking specifies the size of the rapport (the distance between the two images repeating the same pattern), as well as the docking of the wallpaper to be glued.
There are such options for docking:
 Free docking;
 Direct docking;
 Displaced docking;
 Counter docking.
Free docking involves gluing strips without fitting the pattern, the strip can be cut off from a roll of the right size, cutting nothing to fit the strips. In these wallpaper the pattern does not have any clear repetition, and it is not necessary to select a drawing of adjacent canvases. In this case, it is easy to calculate how much material will be needed.
In wallpaper linens with a straight dock, you do not need to shift the canvas to match the pattern. They specify the size of the rapport, that is, the length of the repeating section of the picture. It is only necessary to combine neighboring panels with repeated rapports. For example, we have a ceiling height of 230 cm, wallpaper with a picture with a rapport of 60 cm with a straight dock. One wallpaper strip should have a size of 230 cm, ie 230: 60 = 3,833 rapports, round up to 4 rapports, so that the next canvas starts with a whole rapport. Thus, when pasting such wallpaper with a pattern, one strip will be 230 cm and 10 cm will have to be cut off each time to waste.
If you have specified a displaced docking on the wallpaper you bought, each subsequent strip should be shifted to the offset value indicated on the label. For example, the marking indicates 60/30, ie rapport 60 cm, the displacement value of the figure is 30 cm. At the same dimensions of the ceiling height, we will have to cut off the wallpaper by the size of four rapports and cut another 30 cm to accommodate the shifted pattern. Thus, one strip with scraps will come out 270 cm, and from one 10meter roll of wallpaper it will not be four whole stripes, as in wallpaper with a straight or free docking, but only three (10: 2.7 = 3.7 bands) . If you do not observe the necessary displacement, the wall will not get the correct pattern as a result of gluing all the bands.
There are still wallpaper linens, in which each subsequent strip must be turned 180^{0} in relation to the previous one, so that the result is the correct ornament on the wall. This is quite rare in wallpaper with a geometric pattern.
Conclusion
For the results of the repair to please you, do not regret the time and effort and carefully approach the question of how many wallpapers will be required for repair. It is better to make several calculations using a calculator, roulettes and pens with paper, to resort to the help of store sellers, than to look for the missing rolls or to collect linen from all the remaining scraps and waste. If the calculations are carried out correctly, there will be neither surplus material nor problems with its shortage.

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