Free guide
The words designers use to explain a room, and the numbers they use to get it right. Every line says where it comes from, so you know what’s a rule and what’s a well-earned habit.
Principles make a room work. Your client’s taste makes it theirs. An interior designer brings it all together.
Part 1
What a room is made of, how designers arrange it, and how to describe what you see. This is the vocabulary design schools teach, in plain English.
The room, and the open air between things.
Edges the eye follows. Horizontal calms; vertical lifts.
The outline, and the 3-D bulk: round, boxy, curved.
Hue, value (light to dark) and saturation (intensity).
How a surface feels, or looks like it would feel.
A repeating motif, from small scale to large.
Changes how every color and texture reads.
Textbooks group these a little differently. Some add mass, time, or point, plane and volume.
These seven are the ones accredited interior design programs are expected to teach (CIDA Professional Standards 2024).
Decide what leads. One focal point, then a supporting cast, so the eye knows where to land.
Levels: dominant, subdominant, subordinate. Too many dominant pieces means no emphasis at all.
“The fireplace is the focal point. Everything else supports it.”
How big something is next to the room and the people in it, ceiling height included.
Kinds: visual scale (against the room), human scale (against the body).
“That sectional is out of scale for a room this size.”
How pieces relate to each other and to the whole: shade to lamp base, coffee table to sofa, art to the console below.
Tool: proportioning systems, including the golden ratio.
“The coffee table is in proportion with the sofa.”
Visual weight spread so no side of the room tips. Balance is about weight, not matching.
Kinds: symmetrical (formal, mirrored pairs), asymmetrical (relaxed, different pieces of equal weight), radial (arranged around a center).
“The tall bookcase balances the dark sofa across the room.”
Organized repetition that moves your eye through the room.
Kinds: repetition, alternation, progression (small to large), transition (a curve that leads you), contrast, radiation.
“The brass repeats in three places, so your eye travels the room.”
Everything belongs together: what Francis Ching calls “the pleasing agreement of parts.”
How: a shared palette, material or shape carried through the room.
“The warm woods and the rust tie the room together.”
Unity is what ties things together. Variety keeps it alive. A matched set is unified but often flat; too much variety is busy.
Test: what repeats, and what breaks the pattern on purpose?
“It’s unified by the palette, with enough variety in texture to feel collected.”
Not on the textbook list of principles, but it’s how designers create emphasis and rhythm: light against dark, smooth against rough, straight against curved.
“The black lamp stands out because it contrasts with the white wall.”
The golden ratio is a proportioning system designers and architects have used since ancient Greece: the smaller part is about 62% of the larger. Day to day, designers round it to a number you can measure, about two-thirds. Near, not identical: ⅔ is 67%.
The words people use for how a room feels, what’s causing that feeling, and how a designer creates it on purpose.
Cozy
What’s going onHuman scale and a sense of enclosure; warm, layered light; soft texture.
How designers get thereLamps at several heights with warm bulbs, tactile textiles, seating pulled close.
Airy
What’s going onLight values, generous negative space, pieces with low visual weight.
How designers get thereLight walls, leggy open-frame furniture, bare floor and wall left on purpose.
Calm
What’s going onUnity, a restrained palette, low contrast in value.
How designers get thereFewer colors, close in lightness; quieter patterns.
Pulled together
What’s going onRepetition of a shared color, material or shape creates unity.
How designers get thereAn accent repeated about three times; finishes that echo each other.
Grounded
What’s going onVisual weight kept low; a rug anchors the seating group.
How designers get thereA properly sized rug; heavier pieces kept low.
It pops
What’s going onEmphasis through contrast in value or saturation. It’s the focal point.
How designers get thereOne piece set against a contrasting background, with little around it.
It flows
What’s going onClear circulation; materials and colors carried from room to room.
How designers get there36″ main paths; one color or material repeated through the house.
Cluttered
What’s going onToo many dominant pieces, so no emphasis and no negative space.
How designers get thereOne focal point, edited surfaces, small things grouped into one.
Busy
What’s going onToo much variety, not enough unity; patterns competing at the same scale.
How designers get thereA few repeated colors; patterns at different scales, one large and one small.
Cold
What’s going onA cool palette or cool undertones, cool light, hard and reflective finishes.
How designers get thereWarmer bulbs, wood and textiles, colors with warm undertones.
Something’s off
What’s going onA piece out of scale or out of proportion, or weight piled on one side.
How designers get thereCheck the numbers (rug, art, coffee table), then rebalance the weight.
Part 2
The measurements designers work from, topic by topic. Where established designers disagree by an inch or two, you get the range they share.
Where the eye lands first.
One focal point per area. Start with what the architecture gives you: a fireplace, a big window, a view. No architecture? Make one with large art, a bed wall or a statement light.
TextbookChing: too many dominant elements means no emphasis
Arrange the main seating toward the focal point. Everything else plays a supporting role.
Pro practice
Two stars fighting: a TV and a fireplace on different walls, or a TV stacked over the fireplace with big art beside it.
How people move through a room and sit in it.
Main walkways. The width code requires for a hallway and NKBA sets for a kitchen walkway. No code governs the space between furniture, but this is the number to beat.
The ruleIRC hallway width · NKBA Guideline 7
Paths inside a seating group. 24″ works for a squeeze you don’t use often.
Pro practice
Sofa or chair to coffee table. Close enough to set down a drink. Never closer than 14″.
Pro practice
Between seats in a conversation group. Much farther than 10 feet apart and people stop talking to each other.
Pro practice
Dining table edge to the wall, or a sideboard. 32″ if nobody passes behind a seated person, 36″ to squeeze past, 44″ to walk past.
The ruleNKBA Guideline 8, written for kitchen seating
Of table edge per person. Allow more for chairs with arms.
The ruleNKBA Guideline 9, written for kitchen seating
Beside a bed, to walk and make it. 24″ is the tight minimum.
Pro practice
Float the sofa a few inches off the wall. Pull seating in so it faces itself. Pushing everything to the perimeter leaves an empty middle.
Pro practice
Everything against the walls, and a walking path straight through the middle of the conversation.
Rugs, tables, art and curtains.
Living-room rug: front legs of every main seat on it. Most living rooms need an 8×10 or 9×12. Between two sizes, go bigger.
Pro practice
Dining rug past the table on every side, so pulled-out chairs stay on it. 30–36″ is better.
Pro practice
Bedroom rug past the sides of the bed. A queen usually takes an 8×10; a king, a 9×12.
Pro practice
Coffee table length to sofa length. Never under half. Height at the seat, or 1–2″ lower.
Pro practice
Art width to the furniture below it. The same goes for a mirror over a console or art over a bed.
Pro practice
Floor to the center of the art. Gallery eye level. Most people hang art too high.
Pro practice
Between a sofa back and the art above it (4–8″). Up to 12″ over a headboard. Over furniture, the gap wins over the 57″ rule.
Pro practice
Curtains: rod at least halfway from the window frame to the ceiling, 6–10″ past each side, panels that touch the floor. Skip 84″ panels once the rod goes up.
Pro practice
Small rooms don’t need small furniture. A few well-scaled pieces look calmer than many little ones.
Pro practice
Side table near the height of the sofa arm; nightstand near the top of the mattress, within a few inches. One on each side of a shared bed.
Pro practice
A rug that only fits under the coffee table, so the furniture floats. Close behind: art that’s too small and hung too high.
Layers, bulbs and fixture heights.
Ambient, task and accent. Overall light, light to read or cook by, and light on art or a shelf. At least three sources in a room, at different heights.
Pro practiceThe layer names are textbook terms
What ENERGY STAR calls “warm white” or “soft white.” The look of an old incandescent bulb. 3500–4100K is neutral or cool white; 5000K and up is daylight. It’s printed on the box.
The ruleENERGY STAR bulb labels
Buy brightness by lumens, not watts. 800 lumens is about an old 60-watt bulb; 1,600 is about a 100-watt.
The ruleENERGY STAR
Color rendering: how true colors look under the bulb. Required in California, a good habit everywhere.
The ruleCalifornia Title 24, JA8
Dining table to the bottom of a pendant or chandelier, on an 8′ ceiling. Add about 3″ for each extra foot of ceiling.
Pro practice
Island counter to the bottom of the pendants, about 30″ apart and kept in from the ends.
Pro practice
Keep the bulbs in one room the same color temperature, so lamps and ceiling lights don’t fight.
Pro practice
One overhead light. It flattens everything and makes a home feel like an office. Lamps are the cheapest fix in design.
Making a room feel steady.
Check each wall, and each side of the room. Does one side pull? Find what’s causing it with the list below, then move weight rather than matching pieces.
TextbookChing · Kilmer · Nielson & Taylor
Center the dining table under its light, or the light over the table. A table that drifts off the fixture reads wrong from every seat.
Pro practice
What makes something look heavy Textbook
Size is the obvious one.
A dark chair against a white wall outweighs a pale one.
Saturated and warm colors pull harder than muted, cool ones.
Bold pattern, coarse texture and elaborate detail all add weight.
A skirted sofa reads heavier than one up on legs.
Five small frames hung together act like one big piece.
One object with space around it draws more attention.
Weight counts for more the farther it sits from the middle.
A big dark sofa on one side and nothing of equal weight across from it. Balance it with height, darkness or a group, not a matching sofa.
What makes a room hang together.
One color leads, one supports, one accents. A starting split, not a formula. The older textbook version: the quietest color on the biggest areas, the boldest on the smallest.
Pro practiceTextbook version: Nielson & Taylor
Repeat an accent color or material in a few places, about three, so it looks intentional and leads the eye around the room.
Pro practiceRepetition creates unity (Ching)
Style objects in odd-numbered groups at different heights, so a shelf or table looks collected, not staged. Use pairs when you want symmetry.
Pro practice
Don’t overmatch. Mix eras, woods and materials. One store and one finish everywhere looks flat.
Pro practice
Leave negative space. Not every shelf and surface needs filling. What you leave empty makes the rest look chosen.
Pro practice
Test paint in the room’s own light, with large samples, at different times of day, next to the floors and fixed finishes.
Pro practice
North-facing rooms get the least, coolest light. Skip cool undertones and choose a lighter color (a higher LRV, printed on the back of the paint chip).
Pro practice
A room that feels beige and boring. It usually isn’t the color. It’s missing texture: linen, wood, wool, stone, a little metal.
Part 3
Principles make a room work. Your client’s taste makes it theirs. This is how a designer brings the two together.
Your own taste trained your eye. On a client’s project, you use that eye to read their taste, then apply the principles and numbers to it. Those hold in any style.
Have them show you rooms they love and say what draws them in. Their words matter as much as the pictures.
Dislikes are often clearer than likes. “Nothing too formal” rules out a lot.
Across their pictures, look for the same color, material, shape or mood showing up again. That repetition is their taste, described in design terms.
“You said you want it calm. That’s why we kept the palette close in value.” Start with what they said, then the principle.
Who uses the room, when, and for what. Taste decides how it looks; how they live decides what it has to do.
Scale, balance, light and the numbers don’t change between styles. A traditional room and a modern room can both have the rug too small.
Designing the room you would want. The client should walk in and recognize themselves, done better than they could have done it.
Built into Designer Edge
When you draw a room in Designer Edge, Check layout measures it against the numbers in this guide and flags anything that’s off, marked as a code minimum, a trade guideline or a designer’s rule of thumb. It checks:
Codes and trade bodies. NKBA Kitchen Planning Guidelines (Guidelines 7, 8 and 9); ADA Standards §403.5.1; International Residential Code R311.6 (hallway width); ENERGY STAR Light Bulb Purchasing Checklist; California Title 24, Joint Appendix 8.
Textbooks and standards. CIDA Professional Standards 2024, Standard 11; Ching & Binggeli, Interior Design Illustrated; Nielson & Taylor, Interiors: An Introduction; Kilmer & Kilmer, Designing Interiors; Allen et al., Beginnings of Interior Environments; Pile, Interior Design.
Pro practice numbers are starting points designers measure from, not building codes. Sources vary by an inch or two; this guide gives the range they share. Figures are drawn to real proportions but are illustrations, not construction drawings.