Twenty calculators for the numbers civil and structural engineers work out every week: concrete and steel quantities, lap lengths, beam forces, levels, flows and foundation capacity. Each one shows its working and uses published formulas, and all of them run in your browser, so they keep working on a weak site connection once the page has loaded.
Click a tool to open it on this page. Its own page, linked at the top of the window, explains the method, works through an example and lists the limits you should know about.
- Concrete Volume Slabs, footings, columns, beams, walls and stairs in m³ or yd³. Open calculator
- Cement, Sand & Aggregate Cement bags, sand and aggregate for nominal mixes like 1:2:4 and 1:1.5:3. Open calculator
- Rebar Weight Weight of reinforcing steel in kg, tonnes or lb, metric and US bars. Open calculator
- Stirrup & Bar Cutting Length Cutting length of stirrups, L-bars and cranked bars with bend deductions. Open calculator
- Lap & Development Length Lap and anchorage lengths to Eurocode 2, ACI 318, AS 3600 or IS 456. Open calculator
- Brick & Block Bricks or blocks per wall, plus mortar cement and sand. Open calculator
- Plaster & Paint Cement and sand for plaster, and litres of paint for any area. Open calculator
- Staircase Risers, treads, going and pitch with code checks. Open calculator
- Beam Calculator Reactions, shear force, bending moment and deflection diagrams. Open calculator
- Section Properties Area, centroid, moment of inertia, section modulus and radius of gyration. Open calculator
- Engineering Unit Converter Stress, force, moment, flow, land area (incl. ropani and bigha) and more. Open calculator
- Slope & Gradient Convert percent, degrees and 1 in n ratios, and work out falls. Open calculator
- Land Area from Coordinates Area, perimeter and bearings of a plot from corner coordinates. Open calculator
- Earthwork & Excavation Pit and trench volumes, and cut and fill from cross-sections. Open calculator
- Levelling (Rise & Fall) Reduced levels from staff readings with arithmetic check and misclosure. Open calculator
- Open Channel Flow (Manning) Flow, velocity and normal depth in channels and part-full pipes. Open calculator
- Pipe Head Loss Friction loss with Darcy–Weisbach or Hazen–Williams. Open calculator
- Stormwater Runoff Peak runoff with the rational method Q = CiA. Open calculator
- Bearing Capacity Ultimate and allowable bearing capacity of shallow foundations. Open calculator
- Retaining Wall Stability Overturning, sliding and bearing checks for cantilever walls. Open calculator
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Codes and methods used
- Lap and development length: EN 1992-1-1 (Eurocode 2), ACI 318-19, AS 3600-2018 or IS 456:2000, chosen in the tool.
- Beams: linear elastic analysis with constant EI for simply supported, overhanging, cantilever, propped cantilever and fixed-ended beams, with shear, moment and deflection diagrams.
- Foundations and walls: bearing capacity by Meyerhof, Vesić (with Hansen depth factors) or EN 1997-1 Annex D, and cantilever retaining wall checks for overturning, sliding and bearing with Rankine earth pressure.
- Water: Manning’s equation for channels and part-full pipes, Darcy–Weisbach with Colebrook–White or Hazen–Williams for pressure pipes, and the rational method with the Kirpich time of concentration.
- Surveying: rise-and-fall levelling with the arithmetic check and misclosure, shoelace area with bearings, and ropani and bigha land units.
- Quantities: nominal concrete mixes, brick and block walls with mortar, plaster and paint, rebar weight and bar cutting lengths with bend deductions.
- Stairs: riser and going checks against the US IRC and IBC, the Australian NCC, UK Approved Document K and India’s NBC.
How far you can rely on the results
The maths in these tools is covered by 113 automated checks against hand calculations and textbook cases, such as wL²/8 and 5wL⁴/384EI for a simply supported beam and published lap lengths for each code. A calculator still only knows what you type in, and codes come with national annexes and amendments. Use the results for estimating, checking and learning, and have design work checked and signed off by a qualified engineer.
Tools by topic
Concrete & materials
- Concrete Volume
- Cement, Sand & Aggregate
- Rebar Weight
- Stirrup & Bar Cutting Length
- Brick & Block
- Plaster & Paint
Structural
Surveying & site
- Engineering Unit Converter
- Slope & Gradient
- Land Area from Coordinates
- Earthwork & Excavation
- Levelling (Rise & Fall)
Water & drainage
Geotechnical
Questions people ask
Are these engineering calculators free?
Yes. There is no sign-up and no limit on use. Everything runs in your browser, and nothing you type is sent to a server.
Do they work on a phone?
Yes. The layout changes for small screens, and once a page has loaded the calculators need no internet connection, which helps on site.
Can I print or save a result?
Each calculator has Copy results and Print buttons under the answer. Print to PDF to keep a record with your calculation file.
Studying or working on coursework as well? The free student tools handle PDFs, Word files, citations and word counts.