Flyover Deck Area Calculator

Input Details

Use component width for common road sections, or enter total width directly.

Deck Length

Choose total length, or span count × span length.

Total length

By spans

Total length (m)

Used when “Total length” is selected.

Span count

Used when “By spans” is selected.

Span length (m)

Total length = span count × span length.

Optional Skew Correction

If length is measured normal to skew, you may correct it.

Apply correction

Skew angle (degrees)

Effective length = length ÷ cos(angle).

Wastage / allowance (%)

Adds allowance for overlaps, revisions, and rounding.

Width input mode

Components auto-sums typical deck elements.

Deck Width Components

If you know the overall width, switch to “Direct total width”.

Carriageways

Lanes per carriageway

Lane width (m)

Left shoulder (m)

Right shoulder (m)

Median (m)

Used only when carriageways = 2.

Left walkway / verge (m)

Right walkway / verge (m)

Left parapet (m)

Right parapet (m)

Live width estimate (components)

Carriageway width

14.000 m

Median used

1.000 m

Estimated total width

20.100 m

This is a preview; final uses submitted values.

Direct Total Width

Use when you already have full deck width from drawings.

Total deck width (m)

Results appear above this form after calculation.

Formula Used

Total width (components) = (Carriageways × Lanes per carriageway × Lane width) + Median (if divided) + Left/Right shoulders + Left/Right walkways + Left/Right parapets.
Base length = Total length, or Span count × Span length.
Effective length (optional) = Base length ÷ cos(Skew angle).
Plan area = Effective length × Total width.
Area with wastage = Plan area × (1 + Wastage%/100).

Tip: Use skew correction only when your measured length is normal to skew.

How to Use This Calculator

Pick a length method: total length or by spans.
Select width input mode: components or direct width.
Enter road-section widths from drawings or standards.
Add an allowance percentage if your workflow requires it.
Press Calculate to view area and downloads above.

Use consistent units. All inputs are in meters.

Example Data Table

Scenario	Total length (m)	Total width (m)	Plan area (m²)	Wastage (%)	Area with wastage (m²)
Divided, 2×2 lanes, typical shoulders	120	12.60	1,512.00	3	1,557.36
Undivided, 1 carriageway, no walkways	80	9.10	728.00	2	742.56
Skew corrected (20°) with direct width	100	11.00	1,170.55	5	1,229.08

Examples are illustrative; verify with your project drawings.

Deck area in preliminary estimates

Flyover deck plan area is a fast proxy for formwork, waterproofing, surfacing, and protective coating quantities. Early design teams compare options by keeping the same alignment and updating only widths, allowing rapid cost deltas. For tender checks, the calculator’s “area with wastage” can align with measurement schedules when drawings are still schematic. For reinforcement and concrete volume, area alone is not enough, but it gives consistent scaling across alternatives. Pair it with deck thickness to convert to volume, and with unit rates to produce quick comparative budgets during option selection.

Width breakdown for typical sections

The component method builds total deck width from carriageways, lanes, shoulders, median, walkways, and parapets. This matches how cross sections are detailed in road standards and helps trace every meter of width back to a line item. When you receive a single overall width from the designer, switch to direct width to avoid double counting.

Length selection and skew adjustment

Use total length when the chainage length along the centerline is already known. Use span mode when you have pier spacing and equal spans, then multiply span count by span length. Skew correction is optional and should be applied only if the provided length is measured normal to the skew line; the calculator converts it to a longer effective length using cosine.

Wastage allowances and reporting

A small allowance is often applied to cover overlaps, trimming, construction tolerances, and measurement rounding. Typical planning ranges are 2–5%, but project specifications may require different values. The CSV and PDF outputs store both inputs and computed results, helping reviewers reproduce the calculation and keep an audit trail for approvals.

Quality checks before approving quantities

Confirm all inputs are in meters and represent the same deck segment. Verify divided or undivided configuration, because medians should be zero for a single carriageway. Compare computed total width against the latest typical cross section. If results look high, check lane width, shoulder entries, and skew angle caps.

FAQs

1) What does “effective length” represent?

It is the deck length after optional skew correction. When enabled, the base length is divided by cos(skew angle) to approximate the longer plan length across a skewed deck.

2) Should shoulders, walkways, and parapets be included?

Include every element that contributes to the plan footprint you are measuring, such as shoulders, verges, walkways, and parapets. If your measurement rules exclude an element, set its width to zero.

3) How do I model a flyover with changing width?

Break the alignment into stations where width is consistent, calculate each segment area, then sum the segment totals. This mirrors how quantity sheets handle tapers and transition zones.

4) What wastage percentage is reasonable?

For early estimates, 2–5% is common for overlaps and tolerances, but always follow project specifications or contract measurement rules. Use 0% when you must report strict measured areas only.

5) Can the calculator work in feet and inches?

Enter inputs in meters for correct internal calculations. The output provides both m² and ft² automatically. If you only have feet, convert lengths and widths to meters before input.

6) Why is the median ignored for one carriageway?

A median is used only in divided roadways. With a single carriageway, the separation does not exist, so the calculator sets median contribution to zero to avoid overstating the deck width.