How to Measure Your Walls Before Painting

When it comes to painting your apartment or home, one of the biggest factors in getting an accurate estimate—and avoiding surprises—is knowing your square footage.

I once showed up to an estimate where the client informed me they’d already purchased materials, which turned out to be 1 gallon of paint for the entire apartment. Not exactly going to cut it, I thought.

Whether you’re DIY-ing or hiring professional painters in NYC, correctly measuring your space ensures you purchase the right amount of paint, budget appropriately, and avoid last-minute headaches.

Here’s a simple step-by-step guide on how to measure your apartment or home like a pro and set your painting project up for success.

1. Get the Right Tools

• A tape measure (or a digital laser measure for extra precision)

• A notepad or phone for recording measurements

• A calculator
  

2. Measure Wall Height & Length

Start with one room at a time:

1. Measure the height of the wall from floor to ceiling.

2. Measure the length of each wall.

3. Multiply height × length to get the square footage of each wall.

4. Add all the wall areas together to find the total square footage for that room.

Example: If your room is 8 feet high and 12 feet long, one wall = 96 sq. ft. Four walls = 384 sq. ft.

3. Subtract Doors & Windows

Doors and windows don’t usually get painted, so subtract their square footage. Simply measure and subtract these from your total wall area, or go by the standard measurement:

• Standard door = about 20 sq. ft.

• Average window = about 15 sq. ft.

4. Account for Ceilings (If Painting)

If you’re painting the ceiling, measure its length × width. For example: A 12 ft. × 10 ft. ceiling = 120 sq. ft. Add that into the square footage total to be painted. If you’re not painting (and hiring a pro), be sure to articulate that for accurate pricing.

5. Don’t Forget Trim & Baseboards

Trim, baseboards, and moldings require additional paint (and often a different finish). Measure the length of the trim, then multiply by its width to calculate square footage.

6. Estimate Amount of Paint You’ll Need

You can always ask your paint store rep for help, but a good rule of thumb to keep in mind is:

• One gallon of paint covers about 350–400 sq. ft.

• For darker colors, textured walls, or if you’re covering a strong existing color, expect to need a second coat.

Quick Formula: Total square footage ÷ 350 = gallons of paint needed (per coat).

7. Create a Room-by-Room Breakdown

Write down the total square footage and paint required for each room. This helps painters give you a more accurate quote and allows you to compare prices between companies fairly.

Why This Matters for NYC Apartments

In New York City, where apartments range from cozy studios to sprawling lofts, precision in measurement can make a big difference. Many painting companies price by the square foot or by room size—so the more accurate your numbers, the more accurate (and competitive) your estimate will be.

Pro Tip:

If you’re short on time or don’t want to worry about the math, most professional painting companies (like Undertone Interiors) can do a virtual or onsite measurement for you. But coming prepared with your own measurements shows you’re informed—and helps avoid under- or over-estimating costs.

What Next?

If DIY isn’t your thing, consider hiring a professional to accurately measure, estimate, prep and paint your space for best results. We’ll even help you choose colors and finishes. Reach out to discuss your project and get a free quote / estimate.