How to Build an Interior Design Project Budget | The Index
Guide · Project Management
How to Build an Interior Design Project Budget
From the client's total figure to a working budget that follows the project through design, sourcing and installation.
By The Design Index6 min readUpdated 27 September 2026
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A client gives you a total figure. The project has a scope. Sourcing is about to begin.
The tempting next step is to start finding products. The useful next step is to turn that total figure into a working project budget.
A working budget is more than a list of prices. It shows what the project can afford, what has been estimated, what has been quoted, what the client has approved and what the project has actually committed to spending.
It should become more accurate as the design develops.
Begin with the total project cost
First, establish what the client's number represents.
If the total budget is €100,000, does that include:
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decorative and architectural lighting;
appliances;
artwork and accessories;
tax;
shipping and customs;
receiving, storage and installation;
contingency?
Do not begin allocating money until this is clear. Two people can use the phrase “€100,000 budget” while imagining completely different amounts available for purchasing.
Separate the budget into major cost groups
A useful starting structure might include:
Design and consultant fees
Construction and contractor costs
Fixed finishes and sanitaryware
Kitchen and bespoke joinery
Furniture, lighting and equipment
Window treatments
Artwork and accessories
Logistics and installation
Tax and duties
Contingency
The appropriate categories will depend on the project. The important point is to protect costs that are easily forgotten before distributing the remaining amount between rooms and products.
Protect contingency before allocating the rest
Contingency is not whatever happens to remain at the end. It should be separated near the beginning.
Renovations contain unknowns: concealed conditions, revised measurements, damaged deliveries, additional works and changing lead times. The amount required will depend on the type of project, how much is known and who carries each risk.
Rather than prescribing one percentage for every situation, agree an appropriate allowance with the client and relevant consultants. Keep it visible and avoid quietly using it to fund specification upgrades.
Create room and category allowances
Once the protected project-level costs are removed, distribute the available purchasing budget.
Track it in two ways:
By room: living room, kitchen, primary bedroom, guest room.
By category: seating, tables, lighting, rugs, window treatments, artwork.
The room view helps the designer develop complete spaces. The category view reveals patterns across the whole project. It may show, for example, that decorative lighting or custom joinery is consuming far more of the total than originally intended.
An allowance is a planning figure, not permission to spend blindly. Label it as an estimate until a quotation or selected product replaces it.
Decide where to invest and where to save
Good budgeting is not the same as choosing the least expensive option everywhere.
Identify the project's high-priority moments. This might include:
the sofa used every day;
dining chairs that must withstand heavy use;
the stone visible from the entrance;
exceptional lighting in a restaurant;
high-performance flooring in a commercial space;
one collectible piece that gives the room character.
Then identify areas with more flexibility. A bespoke piece may be balanced by simpler secondary furniture. Expensive wall finishes may be concentrated in one area rather than used throughout.
The budget becomes a design tool when it expresses priorities rather than applying one price level indiscriminately.
Track four different numbers
Every significant budget line should distinguish between:
Budgeted
The amount allocated before the final item or supplier is confirmed.
Quoted
The current supplier or contractor price, normally with a date and stated validity period.
Approved
The amount the client has agreed to proceed with.
Paid
The amount that has actually been invoiced and settled.
These numbers are not interchangeable.
For example, a dining table may have an allowance of €4,000, a supplier quotation of €4,600, client approval at €4,600 and an eventual paid total of €5,050 after delivery.
Keeping the stages separate makes it possible to see both the expected outcome and the project's real financial commitments.
Calculate landed cost, not only product price
The retail or trade price of an item may be only one part of what it costs the project.
Depending on the order, landed cost may include:
product price;
tax;
shipping;
customs duties;
currency conversion;
receiving and inspection;
storage;
delivery to site;
assembly or specialist installation.
Record these costs either against the individual item or within clearly defined logistics allowances. Do not mix the methods without checking that charges have not been omitted or counted twice.
If the exact shipping price is not available, use an estimate and mark it as such. Replace it when the supplier confirms the real figure.
Connect every specification change to the budget
Design develops through revisions. The budget needs to move with it.
When one product replaces another, record:
the previous approved or estimated cost;
the new cost;
the difference;
any change to shipping, installation or tax;
whether the client has approved the change.
A €500 increase may appear minor in isolation. Twenty unrecorded increases can alter the project substantially.
Avoid waiting until the end of a design stage to recreate the financial consequences from emails and notes. Update the budget when the decision changes.
Record client approvals with their financial impact
An approval should identify more than the selected image.
Where appropriate, show:
item and specification;
quantity;
unit price;
estimated additional costs;
total;
effect on the relevant allowance;
effect on the overall budget;
approval date.
This gives the client the information required to make an informed decision and creates a reliable project record.
Keep tax treatment and designer revenue separate
Interior projects can include design fees, hourly work, procurement fees, purchasing commissions, product markups and reimbursable expenses. These should be visible in the studio's financial planning without making the client-facing budget confusing.
How tax and purchasing structures should be handled depends on the business, contract and jurisdiction. Confirm the correct treatment with a qualified accountant or legal adviser.
At an operational level, the studio should still be able to answer:
What belongs to the client's project cost?
What is studio revenue?
What is being paid to a supplier?
What has been invoiced?
What margin or fee is expected?
If those answers only exist in someone's memory, the financial system is not complete.
Review the budget at defined moments
Set formal budget reviews at important project stages:
after the brief and initial cost plan;
at the end of concept design;
before presenting final specifications;
before orders are placed;
during procurement;
before installation;
at project close.
The live budget should be updated continuously, but these reviews give the designer and client a moment to examine the whole project rather than one isolated purchase.
Interior design budget checklist
Confirm the client's total figure
Define exactly what the figure includes
Separate fees, construction, purchasing and logistics
Protect an appropriate contingency
Create allowances by room and category
Identify investment and saving priorities
Track budgeted, quoted, approved and paid values
Include tax, delivery, customs and installation
Update costs whenever specifications change
Record approvals with their budget impact
Review the complete budget at project milestones
Reconcile final invoices and payments at close
The budget should tell the current truth
A perfect original estimate is less valuable than a budget that reflects what is happening now.
Products change. Quotations expire. Quantities are revised. A client decides to invest more in one room and reduce another. None of this automatically means the project is badly managed.
The risk appears when those changes happen in the design but not in the financial record.
A healthy project budget is live, legible and connected to the decisions creating it.
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