Gutter Estimating Software: Downspouts From Drainage Area, Not Eave Length

Trace the eave line once. Get coil by the foot and by the pound, hanger count at your spacing, every corner counted as an inside or outside miter, and downspout count driven by the roof area actually draining into that run.

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Short answer: what is gutter estimating software?

Gutter estimating software lets a gutter contractor measure quantities directly off a PDF plan set instead of a paper scale rule and a spreadsheet. ExitSaaS builds a browser-based takeoff and estimating tool that imports multi-page plan sets, calibrates scale per sheet, and measures linear feet of eave and downspout, each for miters, outlets, elbows and straps. One trace drives a full material and labor assembly with coverage rates and waste built in, and every quantity traces back to a colored mark on a specific sheet. It costs $2,500 one time, and you receive the source code under a perpetual licence — so there is no renewal, no seat count, and no year-two invoice.

The problem: the eave tells you gutter, not water

  • Downspout count comes from roof drainage area, not eave length. A 40 foot eave under a porch roof and a 40 foot eave under half a two-storey hip carry wildly different volumes. Every drop you miss is an overflow the homeowner calls about.
  • Downspout length is on the elevation, not the plan. The plan shows where a downspout lands, not how far it falls. Two houses with identical footprints and identical eave runs can differ by half the downspout material.
  • Every corner is a counted part. A wheel run around a roofline gives one continuous number and loses the miters entirely — and a house with a bay, two dormers and an L-shaped rear can carry eight or ten of them.
  • The right gutter size is regional. Capacity depends on roof area, pitch and local rainfall intensity together, so the same five inch gutter that is comfortable in one region is undersized in another on an identical roof. There is no published K-style capacity chart at all — a K-style has to be sized by its equivalent semicircular area.

Gutter work looks like the simplest linear takeoff there is, right up to the point where the parts list has to be right: miters by hand, outlets one per drop, two elbows minimum per downspout and three where an overhang forces an offset. Expansion joints are their own line, and aluminium moves more than any other gutter metal.

How the tool handles it

Each roof plane is assigned to the eave it drains into, so downspout count and size come from the area actually arriving at that run rather than from its length. Corners are classified inside or outside from the traced geometry and emitted as miters. Storey height is captured with the drop, so downspout feet, stick count, straps and offset elbow pairs fall out of the same measurement.

One trace, the whole material list

A condition is a named, colored layer you trace on the drawing. An assembly turns that one condition into every part it drives, each with its own formula, coverage rate, waste percentage and rounding rule. A Seamless 5in K-style condition looks like this:

Part Unit Driven by
Gutter coilLF / LBeave LF × waste; .027 × 11⅞in coil is 0.377 lb per foot
Hidden hangersEAeave LF ÷ spacing — 24in typical, tighter where ice is long-lasting
End capsEAone per open terminus, left and right are separate parts
MitersEAone per corner, split inside and outside, strip or box
DownspoutSTICK(wall height + elbow offsets) × drop count ÷ 10ft
Outlets / dropsEAequals downspout count, one to one
ElbowsEA2 minimum per downspout, 3 or more where an offset is needed
Downspout strapsEAdownspout LF ÷ spacing
Sealant and rivetsTUBE / EAper miter and end cap joint
Expansion / slip jointEArun LF ÷ 32ft for aluminium (50ft other metals)
Gutter apron / drip edgeLFeave LF
Downspout shoe or kick-outEAone per downspout
Splash blockEAone per ground-level discharge

Change a coverage rate, a waste percentage or a unit cost and every job using that assembly re-prices. You are not editing numbers in twelve places.

Drainage routing, not just length

Each roof plane is assigned to the run it drains into. Drop count and downspout size come from that area, adjusted for pitch — a 6-in-12 roof drains as though it were about ten percent larger than its footprint.

Corners counted as parts

Every direction change in the traced line is classified inside or outside and emitted as a miter with its own sealant and labor, so the corner count is an output rather than something remembered on site.

Two published design maximums, not folklore

SMACNA's practical limit is about 50 feet of gutter served by one downspout, and it caps a run at 50 feet between ends or joints — with the federal spec tightening aluminium to 32 feet because it moves the most of any gutter metal. Both are about thermal movement, and both are easy to miss on a long run.

Every number traces back to a mark

When a callback comes in about an overflow, the marked-up plan shows which roof planes were routed to that run and the drainage area that set the drop count.

Every number on the report links back to a specific mark, on a specific sheet, at a specific place on the page. The marked-up PDF export draws every mark in its condition color with the quantity labeled — that is the file you attach to the bid.

Accuracy is held to a stated tolerance: linear measurements within 0.10% of true, straight-sided areas within 0.25%, and calibration repeatable within 0.20% across five separate calibrations of the same page. Geometry is stored in PDF units, never screen pixels, and rounding happens exactly once — at report time.

What it costs

A missed downspout is a callback, and a callback on a finished gutter run costs more than the drop would have.

$2,500, paid once. Nothing in year two. Nothing in year three. No per-seat bill and no renewal date.

Estimators using it A per-seat subscription, five years Ours, one-time licence
1$8,745 – $10,000$2,500
2$17,490 – $20,000$2,500
3$26,235 – $30,000$2,500
5$43,725 – $50,000$2,500

Their column multiplies by headcount and then repeats every year. Ours does neither. Put a fourth estimator on it and the number is still $2,500, because you are not licensing seats — you are buying the software.

And it does not repeat

Whole company Per-seat subscription, billed that year Ours, billed that year
Year 1$1,749 – $2,000 × seats$2,500
Year 2$1,749 – $2,000 × seats$0
Year 3$1,749 – $2,000 × seats$0
Year 4$1,749 – $2,000 × seats$0
Year 5$1,749 – $2,000 × seats$0

What you actually receive

  • The source code. Not access to it — a copy of it, running on your infrastructure.
  • A one-time perpetual licence. It does not expire, it cannot be revoked, and there is no renewal date in your calendar.
  • No seat count. Put every estimator in the company on it. There is no user tier to outgrow and nothing that counts logins.
  • No dependence on us. Sixty days of support are included. After that you can hire any developer to change it, because you have the code. Most vendors cannot make that offer, because with them you are renting.

Subscription figures are publicly reported PlanSwift prices from software review sites, shown as a representative example of per-seat takeoff pricing. Check any vendor's current pricing directly before you compare. See the full PlanSwift comparison.

What is being built next

  • DXF and DWG import is in active development. Today the tool reads PDF. If your drawings arrive as CAD files, ask on the call and we will give you honest timing rather than a guess on a web page.
  • Auto-count symbol recognition — box a symbol once and find every match on the sheet — is a later release.
  • Multi-estimator assignment, so a supervisor can hand work to specific people, is still being built out.

See it run on your own plan set.

Bring a PDF you have already bid. We will take it off live on a 30-minute call and you can check our numbers against yours. $2,500 one time. Nothing in year two.

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Frequently Asked Questions

The common trade rule is one downspout per 600 square feet of drainage area for a 2x3 and up to 1,200 for a 3x4 — but that rule is built on a heavy design storm, not a one-inch-per-hour figure, so do not read it against capacity numbers quoted at one inch. The published design maximum is SMACNA's: about 50 feet of gutter per downspout, which is about thermal expansion rather than water volume.

It depends on roof area, pitch and your local rainfall rate together. There is no published K-style capacity table — sizing one means matching its cross-section to the nearest semicircular gutter, which puts five inch at roughly 2,500 square feet at one inch per hour and six inch at roughly 3,840. Divide by your local design intensity: at four inches per hour that is about 625 and 960 square feet. The same roof that is fine on five inch in a low-intensity region is undersized on the Gulf Coast.

Both, and it says which. The code basis is the semicircular gutter table in the 2015 plumbing code and earlier, read at the slope you are actually installing — and note the 2018 edition onward replaced that table with gallons per minute. Because the table is written for semicircular gutters, a K-style is sized by equivalent area rather than read straight off it. Mixing the two gives a number defensible in neither.

Because drainage uses an adjusted plan area, not the flat footprint and not the true sloped area. The standard multipliers run 1.00 for flat through 3-in-12, 1.05 for 4 to 5, 1.10 for 6 to 8, 1.20 for 9 to 11 and 1.30 at 12-in-12. That ten percent can push a borderline run from one downspout to two.

Seamless coil is one to one with finished gutter, so start at 200 feet and add waste. In our experience seamless waste runs three to five percent because there are no lapped ten-foot sticks — though ten percent is the common estimating default, and there is no published figure for either. If your supplier sells by the pound, 220 feet of .027 by 11⅞ inch coil is about 83 pounds.

$2,500 once. $0 in year two and $0 every year after. It is not a subscription — it is a one-time perpetual licence, and you receive the source code and run it on your own infrastructure. Sixty days of support are included after launch. For comparison, PlanSwift is now sold as an annual subscription reported at roughly $1,749 to $2,000 per seat per year, which comes due again every twelve months and again for every estimator you add.

Everyone in your company. There is no seat count, no user tier and nothing that counts logins, because you are not licensing access — you are buying the software. Adding a fourth or a tenth estimator does not change the price. This is the whole difference between owning a tool and renting one per head.

Yes. You receive the source code under a perpetual licence and it runs on your own infrastructure. That is what makes the licence meaningful: after the included 60 days of support you can hire any developer to change it, and nothing we do afterwards can switch it off or raise its price.

Yes. It runs in the browser, so it works on Windows, Mac, iPad and Android tablets with no install and no virtual machine. Pen and touch input share the same code path as the mouse, so tracing with a stylus behaves the way tracing with a mouse does.

Linear measurements land within 0.10% of true value, straight-sided areas within 0.25%, and calibration repeats within 0.20% across five independent calibrations of the same page. Geometry is stored in PDF units at full precision — screen pixels never touch the database — and rounding happens once, at report generation.

Not yet — DXF and DWG import is in active development. Today the tool reads PDF plan sets, which is how drawings almost always arrive. If CAD files are how your work comes to you, raise it on the call and we will give you honest timing instead of a promise on a web page.

Takeoff for Other Trades

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