A structural steel takeoff is a count of every steel piece in a drawing set, with a shape, a length, and a weight for each. You work through the set in a fixed order: confirm the drawings and scale, count members from the framing plans, assign a length to each, multiply by pounds per foot, add allowances for connections and waste, pick up misc metals and finishes, then check the total against the schedules. Tonnage is total pounds divided by 2,000.
This guide walks through that order, with a short worked example and the places where takeoffs usually go wrong. To follow along on paper, grab the printable checklist.
Free. Needs a free Steelflo account (also includes 3 free takeoffs, no card).
The checklist is a free download, and it needs a free Steelflo account (no credit card). If you want a spreadsheet to hold the numbers, the free steel takeoff template for Excel works with the same method.
How do you do a steel takeoff, step by step?
1. Review the set and verify the scale
Before you count anything, make sure you have the whole set: every S-sheet, the architectural sheets that mention steel, the specs, and every addendum. Check the revision on each sheet. Then verify the scale against a dimension you can trust, because a plan printed at the wrong size makes every scaled length wrong. If you need a refresher on sheet types and what each one shows, see how to read structural drawings.
Write down the standard (AISC, or a metric standard) and the units. Everything downstream depends on them.
2. Start with the framing plans
The framing plans carry most of the tonnage. Work one level at a time, one member type at a time: columns first, then beams and girders, then bracing, then girts and purlins. Mark every member you count with a highlighter or a PDF markup. A member without a highlight is a member that is not in your bid yet.
Read the general notes before you start. They hold the grades, the "typical" rules, and the "unless noted" rules that change what a label means.
3. Build a member list by shape
Group what you count by designation: W12X26, W16X31, HSS6X6X1/4, L4X4X1/4. Each line gets a mark, a shape, a quantity, and a sheet reference. If the set has a member schedule, count from the plan and check against the schedule; the two should agree. The schedule vs. direct-label article covers what to do when they don't.
4. Assign lengths
Each member needs a length. Take it from dimensions on the plan, from elevations for columns, or from the schedule if it lists lengths. Prefer a printed dimension to a scaled one. Enter lengths in decimal feet (28'-6" is 28.5 ft). Where the drawings give no length, flag the line instead of guessing, and carry an assumption you can defend.
5. Calculate weight and tonnage
For each line:
weight = quantity x length (ft) x weight per foot (lb/ft)
The weight per foot is in the shape designation for wide-flange beams: a W12X26 weighs 26 lb/ft, so a 20 ft piece weighs 520 lb. For HSS, angles, and channels, look up the weight in a catalog or the shape database. The free steel weight calculator does the lookup in your browser, and steel weight calculation formulas covers plates and bars.
Add the lines to get total pounds. Divide by 2,000 for tons.
6. Add connection material
Connection material (tabs, clip angles, bolts, stiffeners) is rarely detailed on the design drawings, so most estimators carry it as a percentage of member weight. The right percentage depends on your shop, the connection types, and the project, so use your own historical number and write it on the takeoff. Where plates are shown with sizes, count them as their own lines instead.
7. Pick up misc metals
Stairs, rails, ladders, lintels, grating, checker plate, bollards, and canopies often live on architectural sheets or in the details, not on the framing plans. This is where many takeoffs lose tonnage. The commercial steel takeoff checklist goes through what to look for on each sheet type.
8. Price in finishes, waste, and stock lengths
Shop primer, paint, and galvanizing are priced by surface area or weight, so note the spec requirement for each member group. Add a waste allowance for plate and bar, and think about stock lengths when you have many repeated lengths. The full list of cost categories is in the steel estimating checklist.
9. Check your work
Cross-check your counts against every schedule, look for duplicate sheets (the same area drawn on an overall plan and an enlarged plan), and make sure existing steel is excluded. Then do a weight sanity check: pounds per square foot of floor area, compared against jobs you have done before. The QA check for a steel takeoff has a fuller version, and the bid day checklist covers the last pass before you submit.
A worked example (illustrative numbers)
This is a made-up small mezzanine frame to show the arithmetic. It is not from a real project, and the lengths and quantities are chosen for easy checking.
| Mark | Shape | Qty | Length (ft) | lb/ft | Total (lb) |
|---|---|---|---|---|---|
| B1 | W12X26 | 6 | 24.0 | 26.0 | 3,744 |
| B2 | W16X31 | 4 | 30.0 | 31.0 | 3,720 |
| C1 | HSS6X6X1/4 | 4 | 14.0 | 19.02 | 1,065 |
| P1 | PL 3/4 x 12 x 12 base plate | 4 | n/a | 30.6 lb each | 122 |
Check one line: B1 is 6 pieces x 24 ft x 26 lb/ft = 3,744 lb. A 3/4 in plate weighs 30.6 lb per square foot (40.8 lb per sq ft per inch of thickness), so a 12 x 12 base plate is 30.6 lb.
- Member and plate subtotal: 8,651 lb
- Connection material at an assumed 10%: 865 lb
- Total: 9,516 lb, or 4.76 tons (9,516 / 2,000)
The 10% is an example figure, not a recommendation. Use your own.
Where takeoffs go wrong
- Counting a member twice because it shows on a plan, an enlarged plan, and a section.
- Counting existing steel on a renovation set.
- Missing misc metals that sit on architectural sheets.
- Trusting a scaled length when a dimension is printed.
- Skipping the addenda, or working from an old revision.
- Mistyping a shape (W21X26 for W12X26). The math works and the answer is wrong, which is why a second look at the biggest lines pays off.
The common steel takeoff mistakes article goes deeper, and why steel takeoffs are hard explains the reasons behind them. For a full walkthrough on a real-looking drawing set, see the structural steel takeoff example.
Where software helps
Counting is the slow part. In Steelflo you upload a PDF drawing set, it draws a box around each steel label it finds, you review the boxes, and you export a BOM or price it. The count is the number of boxes you confirm. You can see what a finished takeoff looks like in the public sample takeoff. Your judgment on scale, scope, and exclusions still decides the bid.
Quick answers
What is a structural steel takeoff? A list of every steel member in a drawing set with its shape, quantity, length, and weight, used to price fabrication and material.
How do you calculate structural steel tonnage? Multiply quantity by length by weight per foot for each line, add the lines to get pounds, and divide by 2,000 to get tons.
How do you estimate structural steel? Start with the takeoff weight, add connection material and waste, then price material, shop labor, finishes, freight, and erection. Exclusions go in the bid letter.
What is the weight of a W12X26? 26 lb per foot, so a 20 ft piece weighs 520 lb.
Do I need software for a steel takeoff? No. A spreadsheet and a disciplined process work for small jobs. Software saves time when the drawing set is large and you bid often.
Where do I get the checklist? The checklist is below. It needs a free Steelflo account, with no credit card.
Free. Needs a free Steelflo account (also includes 3 free takeoffs, no card).
Want the counting done faster? Start a free takeoff on steelfloai.com. A free account, no card, gets you in.