Harth / Free tools
A little less working out.
A little more making.
Practical tools for the details that move a project forward. Calculate, explore, convert and create in your browser, in imperial or metric units.
The tool library
42 tools, six ways to work
Architectural scale calculator
Move between drawing and real dimensions, resize a print, and export a scale bar.
Interactive tool · Free exportRoof pitch & roof area calculator
Convert roof pitch and total the sloping area and covering strips of your roof planes.
Interactive tool · Free exportRamp gradient calculator
Convert rise and run to gradient, angle and sloping length.
Interactive tool · Free exportStair geometry calculator
Find straight-flight riser and tread options using your own design limits.
Interactive tool · Free exportOccupant load & egress worksheet
Calculate occupant loads and width allowances using factors from your chosen code.
Interactive tool · Free exportFeet, inches & construction units
Add mixed feet-and-inch lengths and convert length, area, volume and mass.
Interactive tool · Free exportFloor & wall area calculator
Total rectangular floor zones, wall faces and openings with a labelled plan.
Interactive tool · Free exportFloor joist span calculator
Find the maximum floor joist span for a species, grade, size and spacing, with the bending, deflection and shear limits shown side by side.
Interactive tool · Free exportWood beam & header size calculator
Size a built-up 2x beam or header from its span and the floor or roof it carries, with moment, shear, reactions and every size and ply count checked.
Interactive tool · Free exportLVL & glulam beam calculator
Find the lightest LVL or glulam beam depth for a span and load, using typical published design values for each product.
Interactive tool · Free exportRafter length & span calculator
Work out common rafter length, overhang, stock length and rafter count from run and pitch, then check the rafter span for your size, species and roof load.
Interactive tool · Free exportJoist notch & hole calculator
Check a notch or bored hole in a sawn joist against the IRC depth, length, edge-distance and middle-third limits.
Interactive tool · Free exportWood post & column size calculator
Estimate the axial load a 4x4 to 8x8 wood post can carry with the NDS column stability factor, and the lightest size that works.
Interactive tool · Free exportJoist hanger & connector schedule
Count joist hangers and fasteners for every ledger, beam and header, and check each hanger's reaction against its catalogue rating.
Interactive tool · Free exportCLT floor panel span calculator
Estimate the maximum single span of a PRG 320 CLT floor panel from bending, shear, deflection and vibration, and the thinnest layup for your span.
Interactive tool · Free exportConcrete quantity calculator
Estimate slabs, walls, footings and columns, including waste and premix bags.
Interactive tool · Free exportBrick & block quantity calculator
Estimate masonry units from wall area, openings, joints and waste.
Interactive tool · Free exportTile quantity & layout calculator
Compare an area allowance with a rectangular tile layout and box count.
Interactive tool · Free exportPlasterboard / drywall sheet calculator
Compare sheet orientations and an area estimate for a rectangular wall.
Interactive tool · Free exportPaint quantity calculator
Calculate paint for walls and optional ceilings, including coats and tin sizes.
Interactive tool · Free exportDecking board calculator
Calculate board rows, linear metres and a conservative stock-length order.
Interactive tool · Free exportFence material calculator
Build a material list for separate fence runs, panels or palings and gates.
Interactive tool · Free exportExcavation & bulk materials
Estimate excavation or fill volume and material mass with explicit allowances.
Interactive tool · Free exportSteel & rebar weight calculator
Calculate weights for round bars, plates, hollow sections and entered section masses.
Interactive tool · Free exportInsulation quantity calculator
Calculate coverage and packs for batts or rolls with your waste allowance.
Interactive tool · Free exportBoard foot & lumber calculator
Total board feet, cubic metres and linear feet for a lumber list, on nominal or actual sizes, with waste and cost.
Interactive tool · Free exportWall framing & stud calculator
Count studs, king and jack studs, cripples, headers and plates for one or more framed walls, with corners and openings.
Interactive tool · Free exportScrew & fastener quantity calculator
Estimate deck screws, sheathing nails or drywall screws and boxes from area, framing spacing and fastener spacing.
Interactive tool · Free exportFloor area ratio & site coverage
Calculate FAR and footprint coverage separately against your own planning limits.
Interactive tool · Free exportSun-path diagram generator
Plot the sun for a selected day and both solstices; export SVG, PNG and hourly data.
Interactive tool · Free exportShadow length & overhang calculator
Explore ground shadows and wall shading from entered sun angles and orientation.
Interactive tool · Free exportR-value / U-value converter
Convert thermal resistance and transmittance with explicit SI and US units, or sum a layer stack with surface resistances.
Interactive tool · Free exportEnvelope heat-loss comparison
Compare two envelope schemes by steady-state heat loss, annual degree-day energy and heating cost.
Interactive tool · Free exportMaterial embodied-carbon comparison
Compare material options using EPD factors or illustrative presets, per unit floor area, for A1–A3 or whole life.
Interactive tool · Free exportSolar PV yield estimator
Estimate annual and monthly PV output from capacity and a regional or documented specific yield, with savings and simple payback.
Interactive tool · Free exportSTC & IIC sound rating estimator
Look up typical lab STC and IIC ranges for common walls and floors, or estimate STC for a solid wall from its weight, against your target.
Interactive tool · Free exportMass timber char depth calculator
Work out char depth, effective char depth and the residual section of glulam, timber and CLT after a fire exposure, by NDS or Eurocode 5.
Interactive tool · Free exportRoom schedule & area program
Build an editable room program with counts, areas and circulation allowance.
Interactive tool · Free exportArchitectural rendering prompt builder
Assemble a precise, editable rendering prompt from your design choices.
Editable template · Free exportArchitectural design brief builder
Turn project facts, priorities and constraints into a structured editable brief.
Editable template · Free exportConstruction RFI form builder
Prepare a clear request for information with drawing references and a response field.
Editable template · Free exportMaterial palette & mood-board maker
Arrange local images, name your materials and export a board with sampled colors.
Local images · Free exportYour inputs and files are processed locally. Every tool includes its method, assumptions and an export, and every calculator works in imperial or metric units. Use the outputs as a starting point for your project and verify them against its requirements.
Free online tools for architects, designers and builders
Harth's free tools cover the small calculations and file jobs that interrupt design and construction work: converting a drawing scale, checking a stair, estimating concrete or paint, plotting the sun or drafting an RFI. Each tool opens with a worked example, shows its formula and assumptions, and exports a PDF, CSV, SVG or file you can keep.
Nothing needs installing and nothing is uploaded. The tools run in your browser, so they also work on client and site data you cannot share with a cloud service.
Drawing & geometry
Convert drawing scales, add feet and inches, and work out roof pitch, ramp gradients, stair risers and treads, floor and wall areas, and occupant loads.
Start with: Architectural scale calculator, Roof pitch & roof area calculator, Stair geometry calculator, or see all 7 drawing & geometry tools.
Framing & structure
Estimate joist, rafter and beam spans, size headers, LVL, glulam and posts, check notches and holes, schedule joist hangers and compare CLT floor panels.
Start with: Floor joist span calculator, Wood beam & header size calculator, Rafter length & span calculator, or see all 8 framing & structure tools.
Materials & quantities
Estimate concrete, brick and block, tile, drywall, paint, decking, fencing, excavation and fill, steel and rebar weight, insulation, lumber, wall studs and fasteners, with explicit waste allowances.
Start with: Concrete quantity calculator, Tile quantity & layout calculator, Paint quantity calculator, or see all 13 materials & quantities tools.
Site & solar
Check floor area ratio and site coverage, draw sun-path diagrams for any latitude, and size overhangs and shadows from sun angles.
Start with: Floor area ratio & site coverage, Sun-path diagram generator, Shadow length & overhang calculator, or see all 3 site & solar tools.
Building performance
Convert R-values and U-values, compare envelope heat loss and embodied carbon, estimate solar PV yield, sound ratings and mass timber char depth.
Start with: R-value / U-value converter, Envelope heat-loss comparison, Solar PV yield estimator, or see all 6 building performance tools.
Documents & presentation
Build room schedules and area programs, design briefs, construction RFIs, rendering prompts and material mood boards, then export them.
Start with: Room schedule & area program, Construction RFI form builder, Material palette & mood-board maker, or see all 5 documents & presentation tools.
Frequently asked questions
Are these architecture tools really free?
Yes. Every tool, result and export on this page is free to use, with no account, trial or usage limit.
Do my files or project details get uploaded?
No. Calculations, image processing and exports run in your browser. Inputs and files are not sent to a server, and they disappear when you leave the page unless you save or download them.
Do the calculators work in imperial and metric units?
Yes. Every calculator with dimensions defaults to imperial (feet, inches, pounds, gallons) and has a metric switch. Your choice is remembered across the tools in this browser.
Do these tools check building code compliance?
No. They calculate geometry, quantities and preliminary framing sizes from the values you enter, including any code limits or factors you supply. Framing and structural results are estimates, not designs. Always confirm requirements with the code edition adopted in your jurisdiction, and sizes with the governing span tables or a structural engineer.