How to Estimate Software Development Time: A Practical Guide

According to statistics, about 70% of projects fail to finish on time, making software development time estimation a priority when building a development process. This guide lists basic actions and steps needed to obtain realistic estimates.

1. Why You Need to Estimate Software Development Time

Estimating time lets you know how many hours a project will take, similar to budgeting for opening a flower shop where requirements may change.

You calculate the duration from preparation to launch.

Unexpected issues (e.g., unavailable flowers) require replacements, adding time.

Additional conditions (e.g., storage) may need equipment changes.

New ideas (e.g., selling coffee and books) emerge during planning.

These changes mirror software projects where business needs and initial estimates evolve.

2. Benefits of Development Time Estimation

For clients:

Clear knowledge of delivery dates, crucial for product demos or major events.

Confidence in meeting deadlines.

Control over process and awareness of estimate or budget changes.

For software teams:

Intelligent task/resource allocation and deadline management.

Understanding which experts are needed at each stage.

3. Why Reliable Estimates Are Hard

Estimates often rely on intuition and personal experience, which may not apply to unfamiliar problems, technical uncertainties, or human factors such as illness or unexpected client requests.

Experience may no longer be applicable.

Unpredictable technical issues.

Human factors.

The solution is to use thoughtful methods and proven practices.

4. Estimating Development Time: Stages to Consider

Break the project into phases, estimate each, and sum the results.

Discovery Phase

Gather project information, prepare prototypes, and allocate time for complex technologies.

Receive and review requirements for logical gaps.

Discuss any issues with the client.

Draft a detailed specification and obtain client agreement.

Prepare a clear specification document to avoid costly changes later.

Software Architecture Design Phase

Consider scalability, choose tech stack, class diagrams, databases, libraries, APIs, and sub‑phases.

Development Phase

Divide development into logical sub‑phases to monitor progress; projects may take 2–12 months.

Testing Phase

Include thorough testing from the start to reduce defect‑fix costs.

Additional Time: Buffers and Time‑Eaters

Account for unpredictable work that can add 5%–25% of total time, such as:

Technical unpredictability.

Integration or extension issues.

Team conflicts.

Meetings, approvals.

Productivity loss, etc.

5. Estimating Project Man‑Hours

Sum task estimates, focusing on the average IT professional’s hourly output. Different roles (developers, designers, QA) have distinct task types and speeds.

Key agile terms:

User story: 1‑2 sentences describing functionality.

Story points: effort measure (not hours).

Backlog: list of tasks to achieve goals.

6. Software Development Time Estimation Methods

Two main approaches:

Bottom‑Up / Milestone Reference

Break tasks into sub‑tasks, estimate each, involve developers and an independent expert to validate.

Planning Poker

Team members use cards (1,2,3,5,8,13,21,34,55 or 20,40,100) plus special cards (∞, ?, coffee) to assign story points to user stories. Consensus or discussion resolves differences.

Experience‑Based Method

Compare the new project with similar past projects, adjust for difficulty differences, and multiply by a factor.

7. Sample Estimation Numbers

总时间估算结果（OE）+OE
*缓冲时间 +OE*
时间吞噬者 = 软件开发时间

Example:

5000（OE）+5000
*20%+5000*
20%=7000小时。

Illustrative scenario: estimating effort for an Instagram multi‑account feature.

Design a page with necessary fields.

Determine authentication flow.

Handle redirects based on auth results.

Estimated 13 developer hours plus 3 hours of project‑management coordination.

8. Conclusion

Estimating software development time is not trivial; it requires thorough involvement from the entire team to produce accurate, realistic schedules that satisfy both clients and service providers.

Involving the whole team leverages their experience, improves estimate accuracy, and aligns expectations, reducing the risk of overtime and missed deadlines.

Accurate estimates help control budgets, manage processes, and avoid unpleasant surprises.

If you still don’t know how to estimate product development time, contact us for further discussion.