Working out how many folds and roman blind rods you need before cutting your fabric will save you time and money. You will be left with the correct allowances for the top and bottom hem and enough fabric length for your finished length, and desired a number of folds.
This guide covers calculations of the length of your roman blind and working out the distance between the rods. The measurements give you the position and spacing which dictates how big the folds of your blind will be and their arrangement when the blind is stacked up. At the end of this article, you will be able to work out how far up from the bottom of the blind to put the first rod to get the bottom half-fold the correct size.
What is a Roman blind?
A Roman blind is a rectangular panel of fabric supported on a headrail above the window. When closed, the blind looks flat and rectangular. To open, lift the lower edge towards the top to get horizontal folds across the blind. To prevent the folds from sagging, fit the horizontal rods to the back of the blind at intervals (Blindster.com). These intervals determine the fold depth and the number of folds in a blind.
Close the blind by lowering the cords and opening them by raising them. The blind cords run vertically down the back of the blind, threaded through cord rings attached to the horizontal rods. The cords are guided through a headrail system and locked in any position between open and closed. The headrail system also supports the top of the blind.
Preparing blinds
Make your blind up, lay it out on a flat surface and mark the measurements at the side edges of the blind with pins. Keep the pins close to the edge to avoid unnecessary pin holes in the fabric or lining. Make the folds by bringing the pins together one row at a time, stacking them on top of each other in turn.
By now, you should see how deep the folds look, what the finished stack will be, and if the bottom half fold is the depth. Do not allow the bottom edge of the blind to disappear behind the bottom edge of the first, full fold, or show too much below it.
It has to be level with the first full fold. If not sure about the measurements, recalculate and repeat the pinning procedure until you are happy with the finished proportions. The maximum blind cord allowance is 8′ Foot or 96″/ 2.4 meters.
Roman blinds have their advantages over curtains (Barlowblinds.com). You can make them yourself with the help of visual guides if you are a first-timer.
Calculate the blind dimensions
When you have the finished blind width, length, and preferred Top Section Size, calculate the number of rod pockets on the back of the blind and their positions, determining the style and depth of the blind when pulled up.
The process is the same for all three styles of the blind, but the calculation of rod pocket numbers and their positions differ. Make a standard fold blind where flaps line up in the up position.
How do you determine your headsail allowance?
Establish the Headrail allowance. It should be sufficient to cover the headrail face and allow enough room under the blind for the folds to pull up to the correct position. Use a minimum of 6.5cm for headrail allowance for your headrails and use a minimum headrail allowance of 6.5cm for headrail allowance.
What is the Headrail Allowance?
That is the amount of space by the headrail system for the blind. It depends on the headrail system used. It helps when the fabric cannot be folded up beyond this point, and you still need to calculate the fold sizes.
It is for sidewinder systems that allow 5 to 5.5 cm and for wooden batten and screw eyes that allow 5 – 6 cm. When not sure, measure the profile of your chosen headrail system and add the diameter of your cord guide rings. It also works on the depth of rod pocket tape or the distance from the eyelets to the fold of your rod pocket.
There are different headrails, and you need details about the required headrail system. Specify the safety device, chain break or wall tension device, installation height, and chain length.
Folds calculation
To work out the size of your full fold, divide your blind length by this number. Get the size of your half fold, and divide your full fold length by two.
Steps
- Deduct the headrail allowance from the finished blind length to give the amount of fabric to be folded.
- Divide the length of the fabric by an odd number of fold sections. The amount you get is the fold depth for that number of fold sections.
- Add the headrail allowance to the fold depth to get the Top Section size.
- Find the odd number that gives a Top Section size nearest your preferred Top Section size.
- The closer odd number is your number of fold sections, and the answer you got when you divided the length of fabric in step 2 is now the depth of your folds.
- The number of rod pockets is the number of fold sections divided by 2.
What is the additional depth on the bottom fold?
That is the final fold of the blind that extends further than all the other folds. It helps when you want to display a decorative border or trim at the bottom of the blind. Making the last fold a little longer on standard fold blinds to protect the other folds from sun damage is a personal choice.
The required number of fold sections
Choose an odd number of fold sections, which should be close to the ideal number calculated. Fewer fold sections on a large blind or with a large fabric design can still do. Decide on more fold sections on a narrow blind with a delicate fabric design. Re-enter different values to view the effect on the stacked-up depth, before making your calculations.
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