The arithmetic is a cylinder
The inside of a length of conduit is a cylinder, and its surface area is pi times the bore diameter times the length. A 150 foot run of two inch pipe with a 2.067 inch bore has about 81 square feet of inside surface. Divide that by whatever coverage the lubricant manufacturer publishes and you have a quantity. Everything else on this page is refinement.
The first refinement is that there is a second surface, and on a multi-cable pull it is the bigger one. Four cables at 0.65 inches outside diameter running through that same 150 feet present about 102 square feet between them — more skin than the pipe they are going into. Sizing lubricant on the bore alone quietly understates the job whenever more than a couple of cables are in the pull, which is most of the time.
Where the lubricant ends up is not where you put it
This is the part that matters more than the quantity. Lubricant lowers friction where there is lubricant, and a pull is a machine for wiping it off. Poured into the mouth of the pipe before the pull starts, it coats the entry and the leading cable, and from there it gets carried, spread and scraped away as the cable travels. The far end of a long run may see very little of it.
That is unfortunate, because the far end is where it is needed. Tension multiplies through bends, so the last bend before the pulling end carries the highest tension in the run and produces the highest sidewall pressure against the pipe wall. It is the place where the friction coefficient does the most damage to the numbers and the place least likely to be properly lubricated. The cable pull tension calculator shows the effect directly: change the friction figure and watch what happens to the last bend rather than the first.
The practical consequences are the ones crews already know. Feed lubricant continuously at the entry while the cable moves rather than dumping it in beforehand. Break long runs at a pull point and re-lubricate there, which also collapses the accumulated tension. And carry more than the bare arithmetic says, which is what the allowance field is for.
Coverage figures vary enormously and this page does not have yours
| What changes the coverage | Why it matters to the quantity |
|---|---|
| Thin pourable liquid against a heavy gel | Different film thickness, so different area per gallon by a wide margin |
| Bore size | Surface area grows with diameter, so a larger pipe is a bigger job per foot |
| Number of cables | Cable surface adds up fast and overtakes the bore surface quickly |
| Bends and pull points | Re-application at each break, and more waste at each opening |
| How it is applied | Continuous feeding uses it where it works; front-loading wastes most of it |
None of those have general answers, which is why the coverage field takes your number rather than supplying one. The value sitting in it by default exists so the calculator produces output on first load. It is a placeholder, it is stated as one on the field, and it should be replaced before you order anything.
Compatibility is a manufacturer question
Lubricant sits against the cable jacket for the life of the installation, not just for the duration of the pull. Whether a particular compound is compatible with a particular jacket material, and with the raceway, is published by the people who make each of them. It is not a general property and it is not something a quantity calculator can address. Ask both manufacturers before a large pull, because the failure mode is slow and the cable is in a wall.
Related pages
Fill first: the conduit fill calculator for conductors given by insulation type and trade size, or the low-voltage pathway calculator for cables given by outside diameter. Then the raceway material list on the conduit run take-off calculator, the bend marks on the conduit bend and offset calculator, and the tension itself on the cable pull tension calculator.
The parts this page will not touch
A cable under pulling tension is a spring with several hundred pounds in it. When a rope, a swivel, a grip or an eye lets go, the stored energy comes out along the line of the pull, and everything standing in that line — people first — is in the path. The tension figures on this page exist so you know how much energy is in the system, not so you can decide it is acceptable. Rope, grip, swivel and anchor ratings come from their makers, and the people who set up a pull of any size are the ones qualified to judge it.
A raceway you are pulling into is very often a raceway that has something else in it, and the assumption that a circuit is dead is the assumption that kills people in this trade. Whether a conductor is energised, how that gets established, and who is permitted to work on or near it are matters for a licensed electrician working to the rules adopted where you are. Nothing on this page establishes any of it and nothing here is a procedure.
This page does not supply limits and cannot judge yours. Fill percentages, support and strap spacing, minimum bend radii, tray loading rules, cover depths and every other installation limit come from the code your jurisdiction has adopted and from the manufacturer of the product you actually bought, and the two do not always agree. The arithmetic here runs on figures you type in. Whether the result is acceptable is a conversation with a licensed electrician and with the inspector who signs the job off.
Questions people ask
How much pulling lubricant do I need per 100 feet?
It depends on the bore and on the coverage of the product, so there is no single figure. The arithmetic is pi times the bore diameter in feet times the length, which gives the wetted surface, divided by the coverage the lubricant manufacturer publishes. For a two inch pipe that surface is about 54 square feet per 100 feet of run; what that becomes in gallons is entirely a function of the coverage figure for the product you bought, and this page does not supply one.
Should I size lubricant on the pipe or on the cables?
On whichever is larger, which on a multi-cable pull is almost always the cables. Four 0.65 inch cables in a 150 foot run present around 102 square feet of surface against about 81 square feet for a two inch bore over the same distance. The calculator shows both figures and will size on either or on the larger, so you can see how much sizing on the bore alone would have understated the job.
Is it better to pour lubricant in at the start or feed it as the cable goes?
Feeding it continuously at the entry while the cable moves puts it on the cable, which is what carries it down the run. A slug poured in beforehand coats the mouth of the pipe and the first few feet and much of it never travels. The distinction matters most at the far end of the run, because that is where tension is highest and where a thin or absent film costs the most. A pull point partway along a long run gives you somewhere to re-apply, and it collapses the accumulated tension at the same time.
Will lubricant damage my cable jacket?
That is a compatibility question for the cable manufacturer and the lubricant manufacturer, and both publish the information. It is not a general property and this page takes no view on it. The reason to check rather than assume is that the lubricant stays against the jacket for the life of the installation, so an incompatibility shows up slowly and by then the cable is in a wall or a duct.
How much difference does lubricant actually make to the pull?
It changes the coefficient of friction, which is the input the tension arithmetic is most sensitive to. Because bends multiply rather than add, a change in the friction figure compounds through every bend in the run — so the effect at the pulling end is much larger than the effect on any single segment. Put the friction figure your lubricant manufacturer publishes into the cable pull tension calculator and run it against an unlubricated figure to see the size of it for your particular run.