About InteriorLab
InteriorLab (njfirefly.com) is a small set of free tools that turn "work it out by hand again, then go looking it up again" into "fill in a few boxes, press one button". The site currently holds 36 tools. The site is about: The interior design calculatorsmost sites never built. Everything runs in your browser: no sign-up, no login, nothing you type is uploaded.
Who it is for
Three groups, mostly. First, people who already have the numbers and simply do not want to re-key them into a calculator every time - someone drafting a budget, or an operator who needs a rough figure to align with a colleague in the next ten minutes. Second, people preparing for an exam, an interview, an application, or a document they have to submit, who want a way to test "what if I change this number". Third, teachers, coaches, and leads who need to explain a rule of thumb rather than hand over an answer.
Whatever group you are in, the position of this site is the same: it puts the reasoning in front of you instead of making the decision for you.What a tool returns is a reference value computed from the inputs you supplied. Before you act on it, you still check it against the source material, the situation on the ground, or the official guidance.
How the tools are built
Every tool has an explicit, reproducible method: what goes in, what formula is applied, what comes out. The logic is not hidden - the full calculation is visible in the page source. That buys two things. The result can be checked by somebody else, and if you think a number is wrong you can follow the formula to the step whose assumption does not hold, instead of choosing between trusting it and not trusting it.
Because all of it runs locally, the amounts, durations and ratios you type never leave the device. That matters most for the inputs that describe your own situation.
How the content is held to a standard
Every page has a floor it has to clear: enough body copy that it is not just a form with a button; at least four questions answered, with the three things that actually decide whether a tool is used well written down - how to use it, where people go wrong, and when it does not apply. Where a page states a specific number, a price, a fee or a rule, it says "check the official source" and gives you a route to check it yourself, rather than inventing a number that looks plausible.
Instructions, the verdict labels and the computed result are kept separate. Instructions tell you how to use the tool, the labels qualify what the number means, and the result is the number. Mixing those three is how a conclusion drawn under one set of conditions quietly turns into a general rule, and it is a mistake we keep going back and fixing.
What this site does not do
It does not give medical diagnoses, medication doses, legal opinions or investment advice. The tools help you frame a question better or get the arithmetic right; the conclusion still comes from a qualified professional or from the official source. For outdoor, diving, wildlife, protected-area and border situations, the site provides safety checklists and official contacts only - it does not provide decompression tables, does not certify any depth or weather as safe, and does not explain how to work around regulations.
What changes over time
Tool pages get reviewed: does the logic still hold, is the reference data still current, are the stated limits still true. When the premises of a tool change, the wording on the page changes too, rather than leaving a stale conclusion in place. If a page does not match what you are seeing in practice, the contact details in the footer are the way to tell us.
What is on the site
- Acoustic Comfort Analyzer - Calculate RT60 reverberation time using the Sabine equation. Get speech-music verdict, low-frequency flag, and
- Acoustic Panel Coverage Calculator - How much absorption panel coverage do you need to hit a target RT60? Calculates panel area, distribution hint,
- Air Purifier Sizing - Sizes a CADR by room area, ceiling height, and pollutant type (allergens, smoke, virus). Includes target ACH b
- Artwork Hanging Height Calculator - Compute the centre-line height of hanging artwork by anchor (sofa back, table top, eye level 145 cm, stairwell
- Backsplash Quantity Calculator - Tile count for a kitchen backsplash with outlet, window, and cooktop deductions plus pattern-specific waste. H
- Bathroom Fixture Spacing Checker - Verifies toilet, lavatory, and shower clearances against IRC code and ADA standards side-by-side. Place fixtur
- Biophilic Design Scorer - Score a room on the 14 Patterns of Biophilic Design from Terrapin Bright Green. Not a checklist, a weighted sc
- Ceiling Fan CFM Calculator - Sizes a ceiling fan by room volume and target ACH (4 for residential, 6 for workshop). Includes blade span rec
- Circadian Lighting Planner - Build an hour-by-hour lighting schedule tuned to melatonin and alertness cycles. Outputs Kelvin, lux and inten
- Closet Capacity Calculator - Estimate the linear feet of short hanging, long hanging, shelves, and drawers you actually need based on the c
- Color Temperature Mood Mapper - Convert Kelvin to actual room mood, circadian impact, and recommended use. Goes beyond 'warm vs cool'.
- Color Undertone Identifier - Test a hex code or RGB against warm/cool/neutral undertones. Warns about the greige trap and taupe-mauve cross
- Ergonomic Desk Height Calculator - Computes seat height, desk height, monitor height, and keyboard height by user height, with arm and eye ratios
- Interior Door Size Selector - Recommend interior door size (width, height, clear floor space) by room type and accessibility need. Links to
- Door Swing Clearance Calculator - Visualise the door swing arc and find which furniture pieces fall inside it. Supports 90°/180° swings, left/ri
- Feng Shui Bagua Mapper - Map your floor plan to the classical Bagua and the Western variant side-by-side. Compass calibration included.
- Flooring Direction Optimizer - Recommend plank direction by room shape, light direction, traffic flow, and plank width. Ties to daylight and
- Flooring Transition Calculator - Suggests transition strip type (T-moulding, reducer, end cap, threshold) and undercut need for flush transitio
- Furniture Scale Visualizer - Overlay a 1.70 m human silhouette on a top-down room with preset furniture dimensions (sofas, beds, dining tab
- Mirror Placement Calculator - Find the wall that bounces the most natural light from a window, with cultural context (Feng Shui / Vastu) fra
- Mood Board Palette Extractor - Generate a 60-30-10 color palette from a base hex and a style descriptor. Contrast guardrails for accessibilit
- Paint Sheen Wizard - Recommend paint finish across traffic, moisture, lighting angle, substrate. Beyond generic eggshell charts.
- Pattern Scale Visualizer - Determine whether a wallpaper or fabric pattern repeats at the right scale for your wall area. Different from
- Pendant Light Drop Calculator - Solve for pendant drop length over a dining table, kitchen island, entry, or bedside. Includes sightline rule
- Throw Pillow Insert Calculator - Find the right insert size for a throw pillow cover by desired look (choppy, plump, overstuffed) and fill type
- Reading Nook Dimensions Calculator - Compute the minimum footprint for a chair + side table + lamp combo by user height, reading posture, side tabl
- Rug Size Wizard - Recommend rug dimensions by room type and furniture arrangement (all legs on, front legs on, floating, no furn
- Stair Safety Analyzer - Checks rise/run ratio against IRC code and the 2R+T formula (60–65 cm target). Includes headroom, handrail hei
- Tile Pattern Quantity Calculator - Tiles needed + boxes for floor area, with pattern-specific waste (herringbone ~15% vs straight ~10%). Generic
- Traffic Flow Visualizer - Place furniture rectangles on a room plan and detect choke points (any 60 cm path blocked between doors), plus
- Viewing Distance Optimizer - Recommends TV size and seating distance based on content type, viewing angle preference (THX / SMPTE / casual)
- Material VOC Estimator - Estimate a room's VOC load from selected finishes and furniture. Suggests low-VOC swaps.
- Gallery Wall Layout Calculator - Generates a hanger sheet with nail x/y coordinates for rectangular, salon, linear, and diagonal gallery wall l
- Wallpaper Roll Calculator - Wallpaper rolls needed by wall dimensions, roll width (53 / 70 / 106 cm), and pattern repeat (random / half-dr
- Window-to-Wall Ratio Optimizer - Find the daylight-energy trade-off for your glazing ratio. Factors orientation, U-value, and shading.
- Kitchen Work Triangle Optimizer - Measure refrigerator, sink, and cooktop leg distances, check NKBA guidelines (each leg 1.2–2.7 m, total 3.6–7.
Questions
Do the tools need an account or a payment?
No. Every tool on InteriorLab is free, needs no account, and works before you type anything personal. The numbers you enter are used by the calculation on the current page and are gone when you reload.
Can I treat the output as a final answer?
Not on its own. A tool returns a magnitude under the conditions you typed in. It does not include what it costs to act, what might change while you act, or how the other side behaves. Before spending money, signing, or promising something to a third party, check the result against the source material and the official position.
What is the most reliable way to use these tools?
Follow the order given in the usage section: get your figures onto the same basis first, fill in one field at a time, then calculate. Checking that every unit matches the thing you are actually measuring catches more wrong answers than any other habit, and it takes about ten seconds.
My number does not match what I expected. What should I check?
Three things: that the units agree, that you have not left an optional field blank and accepted its default, and that you recalculated after editing an input. If all three are fine, the likely explanation is that your basis differs from the one the tool assumes - the limitations section on each tool page says what it covers.
Will the pages stay available?
We try to keep them, but the premises of a tool, the reference data and the outside world all move. Pages get reviewed and corrected as that happens. If you need to keep a result long term, take a screenshot and record the inputs you used.
Scope and limitations
This page describes what the tools on this site are built to do. A common mistake is to read a short explanation and treat it as an official specification 鈥?it is not. Every tool here is a calculation aid: it works from the numbers you type in, and it cannot verify whether those numbers are correct, current, or appropriate for your situation.
Where this stops: the tools give you a number and the reasoning behind it. They do not replace professional advice, and they do not know anything about your specific case. Where a decision carries legal, financial, safety or health consequences, check the relevant official source before acting on anything you read here.