Every calculation a project needs, in one place
Architecture is a discipline of small, repeated calculations. You scale a dimension off a drawing, check whether a stair will feel comfortable, estimate how much concrete a slab will take, or confirm a plot's permissible built-up area before sketching a single line. Done by hand or in a spreadsheet, these tasks are slow and easy to get wrong. ArchCalc brings the sixteen calculations practising architects reach for most into a single, fast, free web app — so you can stay in flow instead of hunting for formulas.
What you can calculate
- Drawing Scale Converter: Convert measurements between drawing scales like 1/4" = 1'-0" and metric 1:50, 1:100.
- Stair Geometry: Solve riser, tread, total run and stringer length to meet building-code comfort rules.
- Unit Converter: Switch instantly between metric and imperial length, area and volume units.
- Area Calculator: Compute floor and surface areas for rectangular, triangular and composite shapes.
- Diagonal Calculator: Check squareness and find diagonals for layouts and setting out on site.
- Material & Cost Estimator: Estimate concrete, brick, cement and cost from area or volume inputs.
- Roof Pitch Calculator: Convert between pitch, angle, slope ratio and rafter length.
- Land Area Converter: Convert acres, hectares, sq ft, sq m plus Indian units like bigha and gunta.
- Ramp Slope Calculator: Design accessible ramps to gradient limits with run and rise.
- Paint Quantity: Work out litres of paint needed from wall area and number of coats.
- Lumen Calculator: Size lighting by room area and target lux for the space type.
- Sanitary Fixtures: Estimate fixture counts for occupancy to meet plumbing requirements.
- False Ceiling: Calculate gypsum board, channels and screws for suspended ceilings.
- Drywall Partition: Quantify boards, studs and tracks for partition walls.
- Steel Weight: Find the weight of rebar and steel sections by diameter and length.
- FAR Calculator: Compute Floor Area Ratio and permissible built-up area for a plot.
Who it is for
Practising architects and interior designers use ArchCalc for fast checks during design development and on site. Civil and structural engineers reach for the material, steel-weight and area tools when scoping early budgets. Students and exam candidates use it to learn how scale, pitch and FAR actually work, with results they can sanity-check by hand. Contractors and estimators use the material, paint, drywall and false-ceiling tools to turn drawings into quantities and cost.
How to use ArchCalc
Pick a calculator from the sidebar, enter your known values, and the result updates as you type — there is no “calculate” button to press and nothing to install. Switch freely between metric and imperial units, and copy results straight into your drawings, schedules or specifications. Because everything runs locally in your browser, your inputs never leave your device and the tools work even on a patchy site connection once the page has loaded.
Accurate, but always verify
ArchCalc uses the standard formulas and widely accepted rules of thumb taught in architecture and construction — comfortable riser-to-tread ratios for stairs, accessible gradients for ramps, and conventional coverage rates for paint and plaster. Building codes and material specifications vary by country and municipality, so treat every result as a well-informed starting point and confirm critical figures against your local code and a licensed professional before construction.
Frequently asked questions
What is an architectural calculator?
An architectural calculator is a tool that solves the everyday math of building design — converting drawing scales, sizing stairs and ramps, estimating materials and cost, and working out areas, roof pitch and Floor Area Ratio. ArchCalc bundles 17 of these calculators in one free web app.
Is ArchCalc free to use?
Yes. Every calculator on ArchCalc is completely free, works in your browser, and needs no signup, download or login. Calculations run entirely on your device.
How do I convert a drawing scale like 1/4" = 1'-0"?
Open the Drawing Scale Converter, pick your scale (imperial architectural scales or metric ratios such as 1:50), enter the measured value, and ArchCalc returns the real-world dimension instantly.
Can ArchCalc estimate construction materials and cost?
Yes. The Material & Cost Estimator turns an area or volume into quantities of concrete, brick and cement and applies your unit rates to produce a cost estimate you can use for early budgeting.
Are the results code-compliant?
ArchCalc follows widely used rules of thumb (for example comfortable stair riser/tread ratios and accessible ramp gradients), but building codes vary by country and municipality. Always verify final figures against your local code and a licensed professional.
Does it work on mobile?
Yes. ArchCalc is fully responsive and works on phones, tablets and desktops, so you can run quick checks on site or at your desk.