That’s an excellent and very practical question 👍 — because the costing method affects how transparent and flexible your interior project budget will be. Different designers and firms in Delhi NCR use different methods:

✅ 3 Common Costing Methods in Interior Design

Table of Contents

1. Per Sq. Ft. Costing

How it works: Designer quotes a rate (₹X per sq.ft.) based on carpet area or built-up area.
Pros:
- Simple, easy to estimate upfront.
- Good for quick ballpark budgets (e.g., ₹1,500–₹2,500 per sq.ft. for mid-range interiors).
Cons:
- Can be misleading (you don’t know exact breakup).
- Doesn’t account for material variations (laminate vs acrylic, veneer vs PU).
  👉 Best for rough estimates, not final contracts.

2. Lump Sum Costing

How it works: Designer gives a total number for the entire project (e.g., “Your 3BHK interiors will cost ₹18 lakhs”).
Pros:
- Easy to understand in one figure.
- Good if scope is clear and you trust the designer.
Cons:
- Least transparent — you don’t know where money is going.
- If you change scope, cost variations can get messy.
  👉 Best for turnkey projects with a fixed, detailed contract.

3. Item-Wise BOQ (Bill of Quantities) ✅ Most Transparent

How it works: Designer gives detailed line-by-line costs (wardrobe, kitchen, bed, paint, lights, hardware).
Pros:
- Complete transparency.
- Easy to compare materials, brands, finishes.
- You can add/remove items as per budget.
Cons:
- Takes more time to prepare.
  👉 Best for homeowners who want control & clarity on spending.

💡 What You Should Ask Your Designer

Do you provide all 3 methods (sq.ft., lump sum, itemized) or just one?
Can I get a detailed BOQ with brand & material mentioned?
Is your per sq.ft. rate based on carpet area, super built-up, or built-up area?
Do you give me a budget vs final cost report at the end?
How do you handle cost escalations (material price hikes, design changes)?

⚠️ Red Flags

Only gives lump sum cost without breakup 🚩.
No mention of brands, grades, finishes in costing.
Says “Don’t worry, we’ll adjust later” → usually means hidden charges.

✅ Pro Tip

For rough comparison → use per sq.ft. costing.
For contracts → insist on itemized BOQ with brands.
Always include GST, transport, labour, supervision in the written estimate.

👉 Do you want me to prepare a Sample BOQ Template (Excel) for a 2BHK/3BHK — with columns for item, material, brand, quantity, rate, total — so you can demand the same format from your designer for cost transparency?

How do you calculate project cost — per sq.ft., lump sum, or item-wise?