The Method
Much of what a designer charges for is published rules. Here are ours.
By Anas · Updated October 2026 · every source named; conventions marked as conventions
The secret of professional interior design isn't a secret. Most of it is published, measured and checkable — clearances, ratios, light levels, hanging heights. RoomCalm applies that exact rulebook to your room, and shows you the whole thing.
One photo. Your real room redesigned, free. While buying is paused, the Room Plan that writes these rules out for your room is free too.
Why we publish our homework
Most AI design tools hand you a pretty picture and hope you don't ask how it was decided. We do the opposite. Every RoomCalm plan is built from the rules below, and every rule here is attributed to the body or convention that actually governs it — the NKBA for clearances, lighting-design practice for light (with the IESresidential standard named), the paint industry for LRV. If a plan tells you to hang art at 57″ or leave a 42″ kitchen aisle, you can check exactly why.
Colour & paint
Why the palette agrees with itself, and why the paint code comes with a number.
The 60-30-10 balance
60% a dominant colour (walls, big furniture), 30% a secondary (sofa, curtains), 10% an accent (cushions, art). It's the ratio that makes a room read as composed instead of busy — a long-taught studio and interior-design convention.
Classic interior-design convention (taught in design schools & the trade)
Choose paint by its LRV, not just its swatch
Light Reflectance Value is a 0–100 number for how much light a colour bounces back — it's literally the colour's relative luminance ×100. Designers read it to predict how a paint will behave in a room's light; a high-LRV colour keeps a dark room open, a low one needs extra lamps. Every major paint brand publishes an LRV for each colour.
Composition & scale
The measurements that decide where things go and how big they should be.
Hang art centred at 57 inches
Galleries and museums hang work so its centre sits about 57" from the floor — average human eye height. Over furniture, the bottom of the frame stays 6–8" above the piece. It's the single rule that fixes most 'my art looks wrong' rooms.
Size the rug to the furniture
A rug should run 8–12" past the sides of a sofa, with at least the front legs of every seat resting on it; in a bedroom it extends 18–24" beyond the bed. A rug that floats too small is the most common styling mistake there is.
Established interior-styling convention
Curtains high and wide
Mount the rod 4–6" above the window frame (or two-thirds up to the ceiling) and extend it 8–12" past each side, panels just kissing the floor. It makes the window — and the whole wall — read taller and grander than it is.
Established interior-styling convention
Repeat every finish three times
Any material — brass, black metal, a wood tone — should appear in at least three places around a room. Repetition is what makes a deliberate mix look intentional rather than accidental.
Established interior-styling convention
Light
The change people feel the most — and the one you can put numbers on.
Light in three layers
One ceiling light flattens a room. Professional lighting design layers ambient (overall), task (where you read, cook or work) and accent (a lamp washing a wall or plant) — with warm bulbs at 2700–3000K, and never mixed colour temperatures in one sightline.
Established lighting-design practice
Aim for the right light level per task
A working rule of thumb, not a published standard: budget roughly 20 lumens per square foot of floor for ambient light in a living space, and about 50 per square foot where you work, like a kitchen counter or a desk. It's why a single bulb never feels like enough. The IES sets its own targets differently — as the light that lands on a surface — so treat these as a starting budget for bulbs, not a measurement.
Rule of thumb · the IES's residential practice: ANSI/IES/ALA RP-11-26 ↗
Space & clearances
The gaps that decide whether a beautiful room is actually livable.
NKBA kitchen clearances
Keep 42" of aisle for one cook, 48" where two pass; give each zone its landing counter (15" beside the fridge, 24"+18" at the sink, 12"+15" at the cooktop). These come from the National Kitchen & Bath Association's planning guidelines — the industry's measured standard.
National Kitchen & Bath Association (NKBA) Planning Guidelines ↗
Keep walkways clear
Main paths through a room want about 36"; secondary gaps between pieces, 30"; 30" of clear floor in front of a sink or toilet. If a route feels tight in a render, a piece needs to move — comfort is a measurement, not a feeling.
Where the rules stop
We won't pretend a photo is a tape measure. The layout guidance is advisory until you measure your own room; we give no structural or electrical advice and don't handle installation; and paint on a screen is never exact, so every colour code is a precise starting point you confirm with a tester pot. A great designer earns their fee on the things rules can't capture — sourcing, trades, taste built over years. What we do is make the rule-driven part instant and honest.
The Method — FAQ
Is AI interior design just guessing?
Not the way we do it. Most of what an expensive designer charges for is judgment built on published, checkable rules — clearances, ratios, light levels, hanging heights. RoomCalm applies that same rulebook to your room automatically, and this page shows you every rule so you can verify it yourself.
What's the difference between RoomCalm and an expensive designer?
A designer adds site visits, custom sourcing, trades coordination and taste honed over years — real value we don't pretend to replace. But the core information work — a plan, a palette with codes, a lighting scheme, a shopping list sized to real clearances — is largely these rules applied carefully. That part we can do from one photo, in minutes, for a fraction of the price.
Where do these rules come from?
Real governing bodies and long-established trade conventions: the NKBA's published clearance guidelines, established lighting-design practice (with the Illuminating Engineering Society's residential standard named beside it), paint-industry LRV values, museum hanging standards, and design-studio conventions like 60-30-10. We attribute each one rather than dressing convention up as science.
What are the honest limits?
The layout guidance is advisory until you measure your own room — we work from a photo, not a laser measure. We give no structural or electrical advice and don't do installation. Paint on a screen is never exact, so every colour code is a precise starting point you confirm with a tester pot. We'd rather state that plainly than oversell.
See these rules applied to your room
Upload one photo and see your real room redesigned — free, no sign-up, no card — with what's holding it back and the first thing to change. While buying is paused, the Room Plan for that room — a lighting plan in real lumens and the rules above applied to it — is free too, on every redesign.