18 free calculators for interior designers
Built for the conversations you actually have on site — when you don't have time to Google. AC tonnage, paint, tile, plywood, cut list optimizer, budget estimator, rug size, TV placement, drywall, grout, moulding and more. No signup, works offline once loaded.
Pick a tool
Each calculator opens as its own page — bookmark the ones you use most, or download the InteriorOS app to get all 11 in your pocket.
Interior Design Cost Calculator
Per-sqft budget estimator (India 2026) for Economy, Standard or Luxury finishes. Includes category breakdown.
Most popularAC Tonnage Calculator
Size air conditioning by room dimensions and climate. Get the right ton size for any bedroom, living room, or office in India.
Most popularPaint Calculator
Convert wall surface area into litres of paint needed, by number of coats. Includes door & window deductions.
Plywood Sheet Calculator
Find how many 8'×4' plywood sheets you need for cabinetry, wardrobes or partitions — with waste percentage built in.
NewCut List Optimizer
Optimize your panel cuts with a visual layout per sheet. Handles kerf, grain direction and any sheet size — saves 15–25% in waste.
NewDrywall Estimator
Sheets, joint compound, tape and screws for any room. With door / window deductions.
NewGrout Calculator
Kg of grout for any tiled area based on tile size, gap width and tile thickness.
NewMoulding & Trim
Linear feet for baseboard, crown moulding, chair rail and door / window casing — 10% mitre waste built in.
Most popularTile Calculator
Calculate the number of tiles needed per area with auto-included wastage. Supports any tile size in inches or mm.
Wallpaper Roll Calculator
Get the exact roll count for any feature wall. Standard 53cm × 10m rolls plus custom sizes supported.
Curtain Fabric Calculator
Total fabric metres for any window, factoring in fullness ratio, hem allowance and curtain header style.
Lighting Lumens Calculator
Required lumens by room size and use type. Suggests how many LED bulbs to install for living, bedroom, kitchen or office.
Furniture Spacing Guide
Standard clearances designers reference all the time — sofa-to-coffee-table, dining pull-out, walking aisles, bed gaps.
NewTV Placement Pro
Optimal mount height and viewing distance for any TV size. SMPTE / THX standards used by AV professionals.
NewRug Size Guide
Right rug dimensions for living, bedroom or dining based on furniture layout. Avoid the most common rug-sizing mistake.
Golden Ratio Calculator
Enter one dimension, get the proportional pair (1.618). Useful for room layouts, furniture sizing and frame ratios.
Standard Dimensions
Quick reference for door, window, kitchen counter, cabinet, bed and seating heights — Indian standards.
Unit Converter
Live conversion between feet ↔ meters ↔ inches ↔ centimetres, plus square area conversions for plans.
Made by designers who got tired of Googling on site
Works offline
Once a calculator loads, you don't need signal. Use it on dusty sites and basement showrooms.
Built for India
Hot climate AC sizing, sqft as default, BHK property types, INR pricing in every result.
No signup
Open the page, type, get the answer. No email, no popup, no paywall ever.
Mobile-first
Designed to be used in a client meeting on your phone — large taps, instant results.
Get all 18 calculators in your pocket
Download the InteriorOS app — calculators bundled with project management, finance, CRM and daily site reports. Built for solo designers, firms and agencies in India.