The cost of interior design for a one-bedroom space can vary widely based on several factors. These factors include the location, the level of expertise and reputation of the designer, the scope of work, the type of materials and furnishings selected, and any additional services required. Here are some general guidelines:

Hourly Rates:
- Interior designers may charge hourly rates, which can range from $50 to $200 or more per hour. The total cost will depend on the number of hours the designer spends on your project.
Fixed Fee:
- Some designers prefer to negotiate a fixed fee for the entire project. This fee is based on an estimate of the total hours, resources, and complexity of the project. Fixed fees can range widely depending on the designer’s experience and the scope of work but may start from a few thousand dollars.
Percentage of Project Cost:
- A common method is charging a percentage of the total project cost. Designers might charge anywhere from 10% to 20% or more of the overall project cost.
Room Size and Complexity:
- The size and complexity of the one-bedroom space will influence the cost. Larger or more complex spaces may require more design time and resources.
Materials and Furnishings:
- The cost of materials, furniture, and decor items will contribute significantly to the overall expense. High-end or custom materials and furnishings will increase the budget.

It’s important to note that these are general estimates, and actual costs can vary based on your specific requirements and the market conditions in your area. To get a more accurate estimate, it’s recommended to contact local interior designers, discuss your project details, and obtain quotes based on your unique needs and preferences.