Short answer
A takeoff measures quantities: how many members, what sizes, how long, how heavy. An estimate takes those quantities and adds cost: material, shop labor, coatings, freight, erection, overhead and margin. The takeoff says how much steel there is; the estimate says what it will cost to supply.
Side by side
| Takeoff | Estimate | |
|---|---|---|
| Question answered | How much steel? | How much will it cost? |
| Output | Bill of materials, tonnage | Bid price |
| Inputs | Drawings, schedules, specs | The takeoff plus prices, labor rates, productivity |
| Typical owner | Estimator or takeoff specialist | Estimator, then the owner or chief estimator |
| Can be reused? | Yes, for different pricing scenarios | Only until prices or scope change |
Keeping the two separate matters. A clean takeoff can be re-priced when the mill price moves or when a supplier quotes again. A bid that mixes quantities and prices into one spreadsheet is harder to check and harder to update.
Where the handoff happens
The takeoff ends with a bill of materials: sizes, counts, lengths and weights, usually exported as a CSV or spreadsheet. The estimate begins by applying a price per pound or per ton to material, a labor rate and productivity to fabrication, and line items for detailing, paint, galvanizing, freight and erection.
The shape tables bridge the two. A W12x26 weighs 26 lb/ft, so a 30 ft beam is 780 lb. That weight times the material price gives a material cost, and the weight also drives shop hours. For a worked example see How do you calculate steel tonnage?.
Why mixing them up costs money
When quantity errors and pricing errors are tangled together, you cannot tell which one caused a bad bid. If your takeoff is 6 tons short, every downstream number is wrong by a consistent percentage, and no amount of careful pricing fixes it. If your takeoff is right and the price is wrong, you can fix the price without recounting anything.
It also helps in the other direction. When a GC asks for a number on a revised set, you re-take-off only the changed sheets and re-price the delta. See How do you handle addenda and revisions in a steel bid?.
Do I need both?
For a bid, yes. For a quick budget at 30 percent design, an estimator may skip a detailed takeoff and price from weight per square foot rules of thumb. That is a conceptual estimate and it is only as good as the assumptions. Once the drawings are issued for construction, a real takeoff is what makes the number defensible.
One beam, both steps
Take a single W12x26, 30 ft long.
Takeoff: one piece, W12x26, 30 ft, 26 lb/ft, so 780 lb.
Estimate (example numbers only): material at an example $0.55 per lb is $429. Add shop labor for cutting, drilling and fit-up, connection material, a share of overhead, paint if specified, freight, and erection. Each of those inputs is yours to set.
The takeoff number is fixed by the drawing. The estimate depends on your prices, your productivity and your risk appetite. Two shops can share a takeoff and submit very different estimates.
Can one person do both?
Yes, and in a small shop one person usually does. The danger is letting the pricing mindset affect the counting. If a job looks cheap or expensive, you may subconsciously round quantities. Keeping the steps separate, even in the same hour, helps. Finish the takeoff, export it, then start pricing from the exported list.
Larger shops split the roles so the takeoff specialist focuses on completeness and the estimator on price and risk. Some owners prefer to outsource takeoff and keep estimating in-house, since price judgment is where the knowledge of local conditions matters.
Where does a bill of materials fit in?
The bill of materials (BOM) is the main deliverable of the takeoff: sizes, quantities, lengths and weights, grouped sensibly. It is also what the purchaser uses to order. See How to create a bill of materials. SteelFlo exports the BOM as CSV and Excel, plus an order sheet that groups cuts into stock lengths, so the same data supports both the estimate and the buy.
Look up the sizes
Stop counting steel by hand.
Upload your drawing set and SteelFlo puts a box on every steel label it finds, on every page. You verify the boxes and export a bill of materials.