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Ridge Vent Linear Footage Calculator

Calculate the ridge vent material needed for a roof's ridge line, with waste allowance.

  • Answers as you type
  • Every formula cited
  • Calculated in your browser
SettingsSettings for this calculationUS
Market
Imperial · sales tax
Who is doing the work?

Waste is set to 5% by hand. Pick a tier above to replace it, or keep your own figure.

The combined length of all ridge lines to receive ridge vent.

Measure along the full length of each ridge line where continuous ridge vent will be installed.

Extra material to allow for cut waste at ridge ends and intersections.

5% is typical for a straightforward ridge run; increase it for roofs with more hip/ridge intersections that create more offcuts.

Ridge vent needed

51.45 ft

High confidence
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Show calculation logic

How this was calculated

Formula source(s)

  • Total ridge vent = ridge length × (1 + waste allowance), the standard method for estimating continuous ridge vent material

Inputs used

Total Ridge Length
49 ft
Waste Allowance (%)
5
Final result51.45 ft

What this calculation does not cover

  • Buys vent, not the slot it sits over. A continuous ridge vent only works if the deck is cut back each side of the ridge board — typically 25 to 38 mm (1.5 in) a side — and that slot stops short of the ridge ends, of hips, and of any wall the ridge dies into, with the ridge board itself left uncut. Vent laid over unbroken decking looks exactly like vent laid over a slot and moves no air at all.
  • Leaves out everything that finishes the run. Hip-and-ridge cap runs over the top of the vent as a separate quantity, and because the vent lifts the cap, coverage per bundle is a little less than over a bare ridge. End plugs, the connectors between vent sections and the longer nails that reach through the vent into the deck are all separate line items.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

49 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Part of bigger jobs

This trade is one line of several job takeoffs. Run the whole job and every other trade comes back with it, off the same measurements.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1

Regulatory standards & verification citations1
  1. Total ridge vent = ridge length × (1 + waste allowance), the standard method for estimating continuous ridge vent material
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Tools and safety for this job

To fit the eaves and ridge ventilation. Generic types, no brands, no prices.

Protection this work requires

  • Mineral and glass wool irritate skin, eyes and airways: cover your arms, wear a P2/N95 respirator while cutting, and rinse in cold water — hot water drives fibres in.
  • Most fatal falls on small jobs are from under three metres: use a tower or a ladder tied at the top, and never work off the top two rungs.
  • Knives cause more site injuries than any power tool: cut away from your body, change blades often, and wear cut-resistant gloves to EN 388 level C for repeated cutting.

Fit the eaves and ridge ventilation: Fitting vents and trays is roofing. How much free vent area a roof needs at the eaves and the ridge is set by the regulations or code the work falls under and by the underlay's maker, and this site counts the parts rather than judging whether a roof is ventilated enough.

Show the 5 tools this job needs

Essential

  • Staple gun

  • Tape measure

  • Utility knife

Recommended

  • Cordless drill/driver

  • Crawl boards

Also needed as materials: drill and driver bits, replacement blades, staples.

what each roofing tool is for, and the spec that decides which to buy where one does.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Called something else where you work? Ridge, ridge board and ridge beam — the term in each market, how close the equivalence really is, and the standard that governs it.

Still deciding? Ridge Vent vs Powered Attic Fan — the factors that actually differ, with no invented prices.

Worked example: Shingle roof replacement — step 10 of 11

The data behind it: Production rates by operation

How to calculate ridge vent linear footage in 3 steps

  1. Total Ridge LengthThe combined length of all ridge lines to receive ridge vent.
  2. Waste Allowance (%)Extra material to allow for cut waste at ridge ends and intersections.
  3. Ridge vent neededThe tool computes the ridge vent needed from those figures and shows the formula, its sources, and a confidence rating alongside it.

Ridge vent needed by total ridge length

Page defaults, not your figures above.

Total Ridge LengthRidge vent needed (ft)
20 ft21
40 ft42
60 ft63
80 ft84

Frequently asked questions

Why does intake matter more than the ridge vent itself?
Because a vent cannot exhaust air it cannot replace. With inadequate soffit intake, the ridge vent draws its make-up air through the ceiling below — from the conditioned house — which pushes warm moist air into the roof space. That is the opposite of what it was installed to do, and it is a common finding when a new ridge vent makes a condensation problem worse.
Should intake and exhaust be equal?
Intake should be at least equal to exhaust, and slightly greater is preferred. The convention is a 50/50 split of the required net free area between low and high, with any imbalance biased toward intake. An excess of exhaust is the failure mode; an excess of intake simply means the roof breathes at the eaves.
Can I have a ridge vent and gable vents?
It is usually a mistake. Two high-level exhausts on the same space short-circuit: the ridge vent draws from the gable vent rather than from the eaves, and the lower half of the roof stops ventilating entirely. If a ridge vent is installed, gable vents are normally blocked off.
What is net free area and why is it less than the opening?
It is the effective open area after the baffles, filters and insect mesh inside the vent are accounted for. A product with a 50 mm slot might deliver a fraction of that as usable airflow. Manufacturers publish net free area per linear metre for this reason, and sizing against the physical slot overstates the ventilation by a wide margin.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.