How to Price Interior Design Services: Compare Fee Models With AI

Price from what one billable hour costs you plus your target margin, then choose the model by how firm the scope is: hourly when it will shift, a fixed fee when it is defined, cost-plus when you buy the furnishings. AI prices one project all three ways in a spreadsheet and shows which model protects your margin.

Each model fails in its own way. Hourly billing unsettles clients when hours drift, a fixed fee loses money when revisions pile up, and cost-plus income falls if the client trims the schedule or buys elsewhere. Published ranges are a sanity check, not a rate card: HoneyBook's June 2026 guide quotes roughly $100 to $500 an hour (closer to $100 to $200 in many markets) and 10% to 30% of the total project budget for percentage fees. Your own costs decide where in that spread you sit.

Follow me on Instagram@sagnikteaches

Start with what one billable hour costs you

Take the pay you want from the studio (say $76,000 a year in this illustration), add the yearly running costs ($24,000 for design software, insurance, samples, accounting and marketing), and divide by the hours you can realistically bill. Briefing, sourcing trips, admin and marketing never reach an invoice, so plan on a figure well below the full working year. At 1,000 billable hours, one hour costs this studio $100.

Connect on LinkedInSagnik Bhattacharya

Profit margin goes on top of that, and the arithmetic trips people up. To keep a 25% margin on the price, divide the cost by 0.75: $100 ÷ 0.75 = $133.33. Multiplying by 1.25 gives $125, which is a 20% margin, not 25%. Across 1,000 billable hours that gap is $8,333 of profit that never arrives. Rounding the rate to $135 leaves a margin of 25.9%. The same cost-to-price rule applies to every model below, and the markup versus margin pricing sheet goes through it in more detail.

Subscribe on YouTube@sagnikteaches

One three-room project, priced three ways

A client wants the living room, dining room and main bedroom refreshed: new layouts, furniture, lighting, window treatments and styling, with one installation day. Past jobs and a careful read of the brief suggest 120 hours of your time.

The furnishings schedule comes to $40,000 at your net (trade) prices. Bought at retail, the same items would cost the client about $52,000, so the trade discount is what makes buying through you worth the client's while. Those 52 procurement hours matter later, because they are the work a cost-plus markup has to pay for.

• Model A, hourly. Every hour billed at $135. Furnishings pass through at net cost with no markup.
• Model B, fixed fee. $18,500 for the defined scope: 120 hours plus a 15% allowance for revisions is 138 hours, which is $18,630 at $135, rounded down. Furnishings pass through at net cost.
• Model C, design fee plus cost-plus. $9,200 for the 68 design hours (68 × $135 = $9,180, rounded up), plus a 25% markup on the net furnishings.

One prompt for the three-model sheet, and the slips to fix

Give the assistant every input in one message, say which margin definition you mean, and ask for formulas rather than finished numbers. Any of the main chat assistants (ChatGPT, Claude, Gemini) will work from pasted text, and a free account usually copes with a sheet this small. Swap in your own figures.

I run a one-person interior design studio. Build a spreadsheet layout I can paste
into Excel or Google Sheets that prices ONE project three ways.

Inputs (a labelled block at the top, one value per cell, so I can change them):
- Pay target per year: 76000
- Studio running costs per year: 24000
- Billable hours per year: 1000
- Target profit margin on price: 25% (margin on revenue, not markup on cost)
- Hourly rate I charge: 135
- Estimated hours: 68 design, 52 procurement
- Net (trade) cost of furnishings: 40000
- Markup on furnishings under cost-plus: 25%
- Fixed fee under Model B: 18500
- Design-only fee under Model C: 9200

Model A: hourly, all hours billed at my rate, furnishings passed on at net cost.
Model B: fixed fee, furnishings passed on at net cost.
Model C: design-only fee plus the markup on net furnishings.

For each model show: client total, my revenue, my cost (hours x cost per billable
hour), profit, and margin as profit divided by revenue.
Add four scenario columns: as planned; hours up 30%; furnishings spend down 30%;
both together.
Use formulas, not typed numbers, name every input cell, and list every assumption
you made.

Treat the reply as a first draft. This is the kind of results block an assistant returns, with the usual slips left in (illustrative):

I would fix three things before trusting it. First, the margin column divides profit by cost, which is markup. Margin is profit divided by revenue, so the true figures are 25.9%, 35.1% and 37.5%. Second, Model A's client total reads $60,200, not $56,200: the assistant added a 10% handling fee on the furnishings that nobody asked for and left it out of revenue, so the columns no longer agree. Delete the line or turn it into a labelled input. Third, the "both together" scenario kept the original hours, so rebuild that column from the other two. Asking for a list of assumptions is what exposes slips like the handling fee. If you want more on getting reliable formulas out of a chat assistant, the ChatGPT for Excel guide covers the habits that help.

What each model earns when the project runs to plan

With the slips fixed, the planned case looks like this. Cost is 120 hours at $100.

Model B earns $2,300 more than Model A because of the 15% allowance: the client pays for certainty. If the revisions never come, that allowance is pure margin, so a fixed fee looks good on easy projects and thin on difficult ones.

Model C looks best on paper, which deserves a second look. The 25% markup brings in $10,000 for 52 procurement hours, or about $192 an hour against your $135 rate. A markup floor shows what the buying work alone needs: 52 hours at $135 is $7,020, which is 17.6% of $40,000. The other 7.4 points ($2,980) are payment for risk you carry, such as deposits paid before delivery, damaged or wrong items, returns a supplier refuses and credit terms you extend. If you carry little of that, a client who asks to see the lines will struggle to accept 25%. If you carry a lot, 25% may be too low.

From the client's side, Model A is cheapest and Model C dearest, yet under Model C the furnishings still cost $50,000 against about $52,000 at retail. That gap is what keeps cost-plus defensible. The schedule behind those numbers comes from an FF&E schedule built and checked with AI, so the net cost you feed the sheet is only as good as that document.

Stress test: 30% more hours, 30% less furnishing spend

A plan is the best case. Ask the sheet what happens when the project drifts: hours rise by 30% (156 hours), the client trims the schedule or buys some pieces elsewhere so net purchases fall by 30% (to $28,000), or both at once. Profit and margin, with cost still $100 an hour:

Hourly billing never moves the margin, because revenue follows the hours. The cost sits outside the sheet: a client who cannot predict the final invoice may not sign. The fixed fee breaks even at 185 hours, which is 54% above the estimate, but it slips below your 25% target at about 139 hours, only 16% over. The 15% allowance barely covers that. Holding 25% at 156 hours would need a fee of $20,800 ($15,600 of cost divided by 0.75), about 12% above the $18,500 quoted, which is more insurance than most clients will buy. The usual fixes are to name the number of revision rounds, state the hourly rate for anything beyond them, and say what counts as a change.

Cost-plus is exposed twice. A fixed design fee cannot absorb extra hours, and the markup shrinks with the schedule. In the worst case above, the same project that earned $7,200 earns $600. If the client controls what gets bought, do not let the markup carry the project.

Why a percentage of the budget can leave you short

Some clients ask for a percentage fee because they have seen one quoted. HoneyBook's guide puts percentage-of-cost fees at around 10% to 30% of the total project budget and ties them to full-service design and renovation work. On a renovation the budget includes building work that your hours grow with; on a furnishings-only job the same percentages buy far fewer hours. Fifteen per cent of $40,000 is $6,000, an effective $50 an hour over 120 hours. Twenty per cent is $8,000, or $66.67 an hour. Even 30% ($12,000) only reaches your $100 cost, with nothing left for margin. To earn $135 an hour you would need 40.5% of the furnishings budget.

A percentage works when your hours grow with the budget. When they do not, add a minimum fee, or quote the job on one of the three models above and keep the percentage as a cross-check only.

Wording for each model

Clients accept a model faster when the page says what happens at the edges. An assistant can draft these from your inputs, but edit them to match your own contract, and have a lawyer check the final terms (AI-drafted interior design contracts lists what to look for). Sample wording, with the figures from this project:

Hourly. "My rate is $135 an hour, billed monthly with a time summary. For the three rooms I expect 100 to 130 hours, so $13,500 to $17,550 for design time. I will tell you before we pass 100 hours and again at 130, so there are no surprises. Furnishings are ordered through my trade accounts and passed on at my net price, with no markup."

Fixed fee. "The design fee for the living room, dining room and main bedroom is $18,500, invoiced 40% on signing, 30% when you approve the concept and 30% when you approve the furnishing schedule. It includes the brief, two layout options, two rounds of revisions per room, the sourced schedule, ordering and one installation day. A third round, an extra room or a change after approval is quoted at $135 an hour before I start."

Design fee plus cost-plus. "My design fee is $9,200 for the concept, layouts and specification. Furnishings are ordered at the supplier's net price plus 25%, and every line of the schedule shows the supplier's price, my net price and my markup. I handle delivery problems and returns. Each order is paid before I place it."

Each version leads with the clause that protects the weak point of its model: warning thresholds for hourly billing, a revision count and a change rate for the fixed fee, and open lines plus payment before ordering for cost-plus. Ask the assistant to produce all three from the same inputs so the figures cannot drift between them, then read each one aloud as if you were the client.

Three finished projects through the same models

Your own history tells you more than any guide. Export one row per finished project: the model used, the fee, the markup if there was one, and the hours from your time records. Remove client names and addresses before pasting anything into a chat assistant, and check the model-training switch in its privacy settings; consumer plans let you turn it off.

Here are three finished interior design projects (client names removed). My cost per
billable hour is $100 and my target margin is 25% of revenue.
For each project give: revenue per hour actually earned, profit, margin as profit
divided by revenue, and the revenue I would have needed for a 25% margin.
Then say in plain words where the hours went over and what I should change in the
next quote for each pricing model.
[paste the table]

Illustrative results for three projects:

Project 1 sold a fee that needed $12,533 to reach your target, so the quote was about $2,900 light, and it only just covered costs. Project 2 was priced below today's $135 rate, which is why its margin is 16.7%. Project 3 is the interesting one. A $3,500 design fee plus a $4,400 markup did not pay for 88 hours. To reach 25% with that markup the design fee would have needed to be $7,333, or the markup 37.4% with the original fee. Raising the fee is easier to defend than a markup that high.

The changes that follow are specific. Move the hourly rate to $135 for new clients. Build every fixed fee from hours times rate plus an allowance, and name the revision rounds. For cost-plus, set the design fee so the hours are paid for, and let the markup pay for the buying and the risk. An interior design proposal template is a good place to put the new fee wording once you have settled it.

Checks before you send a quote built on an AI sheet

1. Recompute one cell by hand. Take Model B with hours up 30%: $18,500 minus 156 hours at $100 is $2,900. If the sheet disagrees, find out why before anything else.
2. Search the formulas for the margin column. It should divide profit by revenue. Anything dividing by cost is markup.
3. Nudge one input by 10%. Raise the hours or the markup and watch the outputs move in the direction and roughly the size you expect.
4. Delete assumptions you did not give. Handling fees, tax lines and rounding rules appear when you do not forbid them.
5. Keep inputs in one block. No typed numbers inside formulas, or a changed rate will update half the sheet.
6. Save a dated copy with each quote. When the project finishes, put the actual hours beside the estimate and feed both back into the test above.

How each model gets invoiced

The invoicing pattern is part of the price, because it decides who funds the project. Hourly work is billed monthly in arrears with a time summary, so you are always a month behind your own costs and the client sees the total build up. A fixed fee suits milestone invoices (in the wording above, 40% on signing, 30% at concept approval, 30% at schedule approval), which front-loads cash and gives you a natural point to stop and re-quote if scope changes. Cost-plus carries the most cash risk, since furnishings are the largest numbers on the page. Taking payment before each order is placed keeps your trade accounts from financing the client's sofa.

Put the schedule in the same sheet as the fee. A column for the invoice date and amount under each model lets you see the lowest point of your bank balance during the project, and a second column for the client's running total shows whether the first invoice is bigger than they expect. Ask the assistant to add both columns and to flag any month where your spend on suppliers exceeds the cash collected.

Choosing a fee model from the brief in front of you

Run each new enquiry through the sheet for a quarter, keep the dated copies, and compare them with the hours you actually spent. After a handful of projects you will know which model your own scope habits support, and the sheet will hold numbers drawn from your studio rather than from a guide.

Questions designers ask before choosing a fee model

Should I show a client all three fee models?

Offer one, or two at most, and choose them for this client's scope. Three options make the client do your pricing work and often lead them to pick the cheapest headline number. Use the sheet privately to see which model protects your margin, then present the model that fits how firm the brief is, with an alternative only if the client asks.

What markup should I put on furnishings?

Work it out rather than copying a percentage. Multiply your procurement hours by your hourly rate and divide by the net purchase total: 52 hours at $135 on $40,000 is 17.6%. Add an allowance for the risk you carry, such as damaged deliveries, returns and deposits paid early. HoneyBook's guide says markup-based pricing varies widely and often reflects the purchasing and coordination involved.

Should the first consultation be free?

Price it as the first billable step. A paid concept session of two to four hours at your hourly rate, credited against the project fee if the client signs, filters casual enquiries and starts the brief properly. If you offer a free call, keep it short, say what it covers, and decide in advance what you will not answer without a fee.

Can AI set my hourly rate for me?

It can do the arithmetic and show the margin and markup versions side by side, but it cannot know your costs or your billable hours. Give it your pay target, running costs and time records, ask for formulas, and check one result by hand. The rate it returns is only as good as the billable-hours figure you feed it.

Further reads

• Interior Design Client Questionnaire: Build and Summarise It With AI — A firmer brief makes your hours estimate more reliable.
• Interior Design Project Timeline: Draft Phases and Lead Times With AI — Phase timings that feed the hours column of a fee sheet.
• Interior Designers AI Tool: Check Trade Quotes Against Your Schedule — Check trade quotes against your schedule before ordering.
• AI for Interior Design Studio Admin: Sourcing, Quotes, Updates — Cut the admin hours that never reach an invoice.
• How Much Should a Wedding Planner Charge? Model Fees With AI — The same flat-versus-percentage question for another creative service.
• Consulting Pricing Models After AI: Fixed Fee, Retainer or Value? — Fixed fee, retainer or value pricing for advisory work.
• Interior Design Marketing: Hire an Agency or Do It Yourself With AI? — What an agency and a do-it-yourself AI routine each cost an interior design studio, the weekly hours involved, and five questions that settle the choice.
• Interior Designer Software Compared: Where AI Add-Ons Earn Their Fee — Six interior design tools priced per month, the AI credits worth buying, and a 14-day trial you can run on one finished project.
• Best AI for Interior Design Mockups: Client-Ready Images for a Studio — A six-step studio workflow from a client's room photo to an approved concept image: permissions, prompts, a scale check, labelling and a one-page sign-off.
• ChatGPT for Interior Designers: Ten Prompts for Briefs and Schedules — Ten placeholder-based ChatGPT prompts for an interior designer's briefs, product schedules and client updates, plus the checks that keep prices right.
• Design-Build Proposal Example: A Two-Stage Fee Letter With AI — See a two-stage design-build fee letter with numbers: a stage-one fee built from hours, a stage-two guaranteed maximum price, and AI-drafted wording.
• Home Stager AI: Adding Paid Virtual Staging to Your Service Menu — Four packages, a price built from tool cost and your own minutes, a hybrid physical-plus-virtual offer, and the disclosure wording to use.
• AI Tools and AI Development: The Complete 2026 Guide — the AI hub, including every tutorial in the AI-for-business series.

Sources: HoneyBook's guide to pricing interior design services (3 June 2026) for the published ranges quoted. Every project figure in the worked example is illustrative.