Rebar Weight Calculator
Need to know how much your rebar weighs? Pick the bar size, enter the length and quantity, and this tool calculates the total weight in pounds.
Standard Rebar Weights by Size
Rebar weight depends entirely on diameter. Steel density is constant, so a thicker bar always weighs more per foot. The relationship is not linear because cross-sectional area grows with the square of the diameter. Doubling the diameter quadruples the weight.
Common sizes and their weights per foot: #3 (3/8 inch) weighs 0.376 lbs/ft, #4 (1/2 inch) weighs 0.668 lbs/ft, #5 (5/8 inch) weighs 1.043 lbs/ft, #6 (3/4 inch) weighs 1.502 lbs/ft, #7 (7/8 inch) weighs 2.044 lbs/ft, and #8 (1 inch) weighs 2.67 lbs/ft.
These weights apply to standard carbon steel rebar. Stainless steel and galvanized rebar have slightly different densities, but the difference is small enough that standard weights work for most estimates. If you need exact weights for engineering calculations, consult the manufacturer's specs.
Why Rebar Weight Matters
Shipping cost for rebar is based on weight, not piece count. A truckload of #8 bars weighs far more than the same number of #3 bars, driving up freight charges. Knowing total weight before ordering helps you compare supplier quotes and avoid surprise delivery fees.
Handling safety is another reason to calculate weight. A single 20-foot length of #8 rebar weighs over 50 pounds. Moving dozens of these bars requires equipment or multiple workers. Lighter #4 bars are manageable by hand, which speeds up installation and reduces labor cost.
Structural engineers specify rebar by total steel tonnage for large pours. Knowing the weight helps verify that the delivered material matches the design. Undersupplying steel compromises the slab's strength. Oversupplying wastes money but does not improve performance beyond the design threshold.
Estimating Total Weight for a Project
Start by calculating the total linear feet of rebar your project requires. If you are building a grid, multiply the number of bars running each direction by the length of the slab in that direction. Add the two totals together, then add extra for overlaps at joints.
Once you have total linear feet, multiply by the weight per foot for your chosen rebar size. This gives you the total weight. Divide by 2000 to convert pounds to tons if your supplier quotes tonnage pricing.
Example: A 30×40 foot slab with 18-inch rebar spacing in both directions requires roughly 1,600 linear feet of #4 rebar. At 0.668 lbs/ft, that is 1,069 pounds, or just over half a ton. Ordering a full ton leaves room for waste and ties, ensuring you do not run short.
Frequently Asked Questions
How much does #4 rebar weigh per foot?
#4 rebar weighs 0.668 pounds per linear foot. A standard 20-foot length weighs about 13.4 pounds.
What is the difference between rebar sizes?
Rebar size numbers indicate diameter in eighths of an inch. #3 is 3/8 inch, #4 is 1/2 inch, #5 is 5/8 inch, and so on. Larger bars are heavier and stronger.
Why do I need to know rebar weight?
Knowing weight helps estimate shipping costs, determine if you can handle the bars safely, and calculate the total steel tonnage for structural engineering requirements.
Does epoxy-coated rebar weigh more?
Epoxy coating adds minimal weight, typically less than 1% of the bar's mass. Use the same weight values for both bare and epoxy-coated rebar.
How do I calculate the weight of a rebar grid?
First calculate total linear feet of rebar in the grid, then multiply by the weight per foot for your chosen bar size. This calculator does both steps if you enter the total length and quantity.