Free Construction Calculators
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Free, IS code-based calculators for steel, bricks, paint, and more. Built for Indian construction teams — instant quantity estimates, no spreadsheets needed.
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🏛 Column
One-Way Slab
Two-Way Slab
Column Dimensions
IS 456
Column Height
3000 mm
Slab Thickness
150 mm
Column Size (a)
450 mm
Column Size (b)
300 mm
Main Bar Dia
20 mm · 4 nos
Stirrup Dia
8 mm @ 150
Calculated Result
Ready
65.55
Main bars (kg)
18.42
Stirrups (kg)
83.97
Total weight (kg)
₹5,040
Est. cost
Formula: D² ÷ 163 · IS 456:2000 compliant · includes 5% wastage
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All formulas follow IS code. Results are instant.
Steel and RCC
AI
Steel Calculator for Column
Enter column size, bar dia, and stirrup spacing — get main bar weight, stirrup weight, and total steel per IS 456.
Main bar kgStirrupsTotal kgEst. cost
Top View — Slab Plan
L = 4 m
B = 3 m
Main 10Ø
Dist. 8Ø
Main: 58.3 kg
Total: 80.4 kg
Steel and RCC
AI
Steel Calculator for One-Way Slab
Enter span, width, and bar dia — get main bars, distribution bars, cranked bar lengths, and total steel per IS 456.
Main barsDist. barsTotal kg
Reinforcement Mesh — Both Directions
IS 456:2000
Lx bars
Ly
Lx — 77.3 kg
Ly — 80.5 kg
Steel and RCC
AI
Steel Calculator for Two-Way Slab
Enter Lx, Ly, and thickness — get reinforcement in both directions, top bars, and total weight per IS 456:2000.
Lx barsLy barsTotal kg
Mark
Description
Cut.L (m)
kg
B1
20Ø straight × 4
5.24
52.4
B2
12Ø cranked × 8
3.86
27.5
B3
8Ø stirrup × 32
1.18
15.0
T1
10Ø top × 4
5.24
16.2
Total steel
111.1 kg
Steel and RCC
AI
Bar Bending Schedule Calculator
Enter member details — get a complete BBS with bar mark, shape code, cutting length, and total weight. AI-assisted.
Cutting lengthBar scheduleWeight/mark
English Bond — 4.5 inch wall
5m×3m wall needs
825 bricks
Masonry
Brick Calculator for Wall
Enter wall size and thickness — get brick count, order quantity with wastage, mortar volume, cement, and sand required.
Brick countMortar volOrder qtyCement + sand
Wall Cross-Section — 4×5m Room
Wall surface
110 m²
Putty (2 coats)
84 kg
Primer (1 coat)
12.2 L
Paint (2 coats)
17.2 L
Finishes
Paint Quantity Calculator
Enter room dimensions and coat count — get exact putty, primer, and paint quantities in kg and litres with door and window deductions.
Putty (kg)Primer (L)Paint (L)Surface m²
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FAQ
Questions about these calculators
Yes, completely free. No sign-up, no login, no limit on how many times you use them. All calculators on this page are built and maintained by Onsite and are available to anyone working in Indian construction.
All steel calculators use IS 456:2000 formulas. The unit weight formula is D² ÷ 163 (kg/m), where D is bar diameter in mm. Lap lengths are calculated as 50D for columns. Stirrup cutting lengths account for 90° and 135° bend deductions as per IS standards. The Bar Bending Schedule calculator also follows SP 34 guidelines for shape codes.
A one-way slab (Ly/Lx greater than 2) carries load in the shorter direction only. Main bars run along the shorter span; distribution bars run in the longer direction. A two-way slab (Ly/Lx of 2 or less) carries load in both directions, so main reinforcement is needed along both Lx and Ly. Use the one-way calculator for beams spanning in one direction and the two-way for panels supported on all four sides.
Yes. The brick calculator adds a 10 mm mortar joint to both length and height when counting bricks. It also calculates wet and dry mortar volume separately, then breaks that down into cement bags and sand quantity using a 1:6 mix ratio. Wastage is adjustable — the default is 10%, which covers standard site cutting. Decorative or diagonal brickwork should use 15 to 20%.
The paint calculator uses standard coverage rates: putty at 1.3 kg per m² for two coats, primer at 9 L per m² for one coat, and finish paint at 6.5 L per m² for two coats. These match the coverage figures used by most Indian paint brands on their technical data sheets. Results will be close to actual consumption for smooth plastered surfaces. Textured or rough surfaces will use more — add 10 to 15% in those cases.
It generates a complete BBS table with bar mark, bar type, diameter, shape code, cutting length, number of bars, and total weight per bar mark. The output follows the format used on most Indian construction sites and can be exported for procurement or site use. The AI layer helps verify shape codes and flag common input errors before you finalise the schedule.
Yes. All calculators are mobile-first and work on any browser without downloading an app. Site engineers and supervisors can use them directly from the field on a phone. Results load instantly without any page reload.
These calculators give you a number. Onsite ERP manages what happens after that number — procurement orders, material receipts, vendor bills, labour attendance, progress tracking, and live P&L across every project. If you find yourself doing these calculations daily and then manually entering results into Excel or WhatsApp, Onsite replaces that entire workflow. The calculators are free because we want to be useful to every construction team, whether or not they use Onsite.
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