Rebar Calculator
Estimate rebar quantity, linear feet, weight, 20 ft sticks, laps, and material cost from your slab dimensions and selected spacing.
Slab Dimensions
Rebar Settings
Material Cost
Material Layout Preview
This drawing is a visual material-layout preview. It is not a structural drawing or a building-code compliance check.
Results
Rebar Schedule
| Direction | Bar Size | Spacing | Bars | Approx. Bar Length | Total LF | Weight / ft | Est. Weight |
|---|---|---|---|---|---|---|---|
| Calculate to generate the schedule. | |||||||
Calculation Details
Bar count: for each calculated direction, the estimate uses ceil(relevant perpendicular dimension ÷ spacing) + 1.
Linear feet: number of bars × approximate bar run length. A user-entered waste/overlap percentage is then added to the base material length.
Weight: estimated linear feet × nominal weight per foot for the selected bar size.
20 ft sticks: estimated material length ÷ 20, rounded up to a whole stick.
Cost: estimated 20 ft sticks × stick price, or estimated weight × price per pound, depending on your selection.
Lap/splice information is shown as a material estimate based on the lap length you enter. This calculator does not determine required structural lap lengths.
Material estimate only: This calculator estimates rebar quantity, length, weight, laps, and material cost from the values entered. It is not a structural design, engineering, inspection, or building-code compliance tool. Verify project-specific requirements independently before purchasing or placing materials.
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Example: Estimating Rebar for a Rectangular Slab
Suppose you want to estimate the amount of rebar for a rectangular slab measuring 20 feet long and 30 feet wide. For this example, we will use #4 rebar spaced 12 inches apart in a two-way grid.
These measurements and settings are used only to demonstrate the calculator. They are not recommendations for a particular construction project.
Start by entering the slab dimensions. Set the length to 20 feet and the width to 30 feet. Select #4 rebar, choose 12-inch spacing, and select the two-way grid option.
The calculator uses these measurements to estimate the number of bars running in each direction.
With 12-inch spacing, the example uses approximately 31 bars along the 30-foot dimension and 21 bars along the 20-foot dimension, assuming the bars are counted at both ends.
Calculating the Total Linear Feet
Once you have the estimated bar counts, you can calculate the total length of rebar.
First direction: 31 bars × 20 feet = 620 linear feet
Second direction: 21 bars × 30 feet = 630 linear feet
Add the two amounts together:
620 + 630 = 1,250 linear feet
The estimated base quantity is therefore 1,250 linear feet of rebar, before adding any waste or overlap allowance.
Adding a Waste Allowance
Extra material may be needed to account for cutting waste and other material allowances. If you enter a 10% waste allowance, the calculation becomes:
1,250 × 1.10 = 1,375 linear feet
The adjusted estimate is 1,375 linear feet.
This percentage is only an example. The appropriate allowance depends on the project, cutting requirements, and other material considerations.
Estimating Rebar Weight
The calculator can estimate the total weight using the nominal weight per foot for the selected bar size.
For standard #4 rebar, the nominal weight is approximately 0.668 pounds per linear foot.
Using the adjusted length:
1,375 × 0.668 = 918.5 pounds
The estimated rebar weight is therefore 918.5 pounds.
This is a calculated material weight, not a guaranteed delivery weight. Actual quantities may differ depending on the bars purchased and the final cutting or fabrication plan.
Estimating the Number of 20-Foot Sticks
If you plan to purchase rebar in 20-foot lengths, you can divide the estimated total length by 20.
1,375 ÷ 20 = 68.75 sticks
Rounding up gives approximately 69 sticks of 20-foot rebar.
Keep in mind that this is a simple length-based estimate. The actual number of sticks needed may differ because bars must be cut to suitable lengths, and offcuts may not always be reusable. Lap lengths and other project-specific requirements can also affect the final quantity.
Estimating Rebar Material Cost
The calculator can also help estimate material cost when you know your supplier's price.
For example, suppose a 20-foot stick costs $15. Using the estimated quantity of 69 sticks:
69 × $15 = $1,035
The estimated material cost would be $1,035.
If your supplier charges by weight instead, you can use the price-per-pound option, if available in the calculator.
For example, at a hypothetical price of $0.80 per pound:
918.5 × $0.80 = $734.80
The estimated material cost would be $734.80 based on the calculated weight.
These prices are for illustration only. Rebar prices vary by supplier, location, bar size, and order quantity. Enter a current supplier price for a more relevant estimate.
What This Example Demonstrates
This example shows how the Rebar Calculator can turn slab dimensions and selected settings into an estimated material quantity and cost.
The calculation follows this process:
Slab dimensions → bar count → total linear feet → waste allowance → estimated weight → stick count → material cost
You can change the dimensions, bar size, spacing, waste allowance, or price to explore different estimates.
Important: This calculator estimates rebar quantities, weight, and material costs based on the information entered. It does not determine the correct bar size, spacing, lap length, or reinforcement design for a specific slab. Follow the project plans and applicable requirements, and consult a qualified professional when necessary.
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