Ask three development teams to estimate the same project and you may receive three very different numbers. One is low enough to be tempting, one is in the middle and one looks alarmingly high. As a founder without a technical background, you are left wondering which is right, whether any of them can be trusted and how you are supposed to plan a budget around them.
The frustrating truth is that estimating software is hard, even for experts. Software is a creative, knowledge-based activity with many unknowns, and no two projects are alike. But "hard" does not mean "guesswork". There are sound methods for producing reliable estimates, clear reasons why they go wrong, and practical things you can do to get a number you can genuinely plan around. This guide explains them in plain language. For typical figures by project type, our cost guides give indicative ranges; this article focuses on how those numbers are arrived at.
Why estimates are hard
Understanding why software estimates are difficult helps you interpret them sensibly.
- Requirements are rarely complete. Even careful briefs leave gaps, and details emerge during the work.
- Unknowns are hidden. Integrations, data quirks and edge cases often reveal themselves late.
- Nothing is identical. Unlike construction, each project differs, so past experience only partly predicts the future.
- People vary. Productivity depends on the individuals and how well they work together.
- Change is normal. Users give feedback, markets move and priorities shift.
- Optimism is human. People tend to imagine the smooth path and underestimate the work around it: testing, review, fixes, deployment and communication.
A good estimate does not pretend these things away. It acknowledges them and manages them.
Estimate, quote and commitment are different
These three words are often used interchangeably, and mixing them up causes most of the arguments.
- An estimate is a reasoned prediction of effort and cost, usually a range, based on current knowledge.
- A quote is an offered price for a defined scope.
- A commitment is an agreement to deliver specific results for a specific price by a specific date.
An early estimate is a planning tool. It is not a promise. A fixed price is possible, but only once the scope is defined clearly enough to price firmly, and a fixed price for vague requirements is either heavily padded or a source of later disputes.
How professionals build estimates
Several methods exist, and good teams combine them.
Breaking the work down
The most basic method is to split the project into smaller pieces, estimate each and add them up. Smaller pieces are easier to judge than a whole product. A typical breakdown covers:
- Discovery and planning
- Design
- Each feature or module
- Integrations
- Testing and quality assurance
- Deployment and handover
- Project management and communication
If an estimate does not include the last few items, it is incomplete.
Comparing with similar work
Experienced teams compare your project with ones they have built before. "This portal resembles the booking system we delivered last year, with two extra roles and a payment integration." Past examples ground estimates in reality, which is one reason industry experience matters; see how to choose a software development company.
Using ranges
Honest estimates are ranges, such as "$20,000 to $30,000", not single numbers. A range reflects uncertainty. A single precise figure given early suggests either a guess or a padded price.
Teams often describe a best case, a likely case and a worst case, then work from the likely range, with a contingency for unknowns.
Adding contingency
Because unknowns exist, responsible estimates include a buffer, commonly 10 to 25 percent depending on how well-defined the project is. Clearer requirements justify a smaller buffer. If an estimate has no contingency, the project will probably either go over or cut corners.
Re-estimating as you learn
The best estimates are not one-off. They are refined at each stage, becoming more accurate as uncertainty shrinks. A discovery phase, a prototype or the first development cycle all reduce unknowns and improve the next estimate.
The cone of uncertainty
A useful mental model is that early estimates are inherently wide, and they narrow as the project progresses. At the idea stage, the true cost could be half or double the first guess. After requirements are defined, the range tightens considerably. After a working prototype or several delivered cycles, it tightens further.
This is why a fixed price on day one is risky for both sides, and why staged work, where each stage is estimated separately, is popular for evolving products. We describe this staged approach in what is an MVP.
What drives the number
Whatever method is used, a handful of factors dominate the result. Knowing them lets you see why quotes differ.
- Scope. The number and complexity of features.
- User roles. Each type of user needs its own screens, permissions and testing.
- Integrations. Each outside system adds work and risk.
- Design depth. Standard interfaces versus a fully custom design.
- Platforms. Web, iOS, Android, desktop, or several.
- Security and compliance. Sensitive data and regulated sectors need extra care.
- Data migration. Moving existing records into a new system.
- Scale and performance. How many users and how much data.
- Quality expectations. Testing depth and documentation.
- Team experience. Senior teams cost more per hour and often less per result.
If two quotes differ widely, compare these factors first. The difference is usually in scope assumptions, not in skill or pricing. The articles on mobile app cost and custom software cost show how these factors play out in specific cases.
How to help developers estimate accurately
You influence the quality of the estimate more than you might think. The more clearly you describe what you need, the more accurate and comparable the answers.
Prepare:
- The problem and the goal. What is going wrong, and what should improve?
- The users. Who they are and what they need to do.
- The must-haves and the later list. What the first release needs, and what can wait.
- Examples. Screenshots, sketches or competitor products that show what you mean.
- Integrations and existing systems. Everything the software must connect to.
- Constraints. Deadline, budget range, technology preferences and regulations.
- Decision makers. Who approves what, and how quickly.
A short, clear brief, as described in how to write a software requirements document, is often enough. Sharing a budget range is also helpful. It is not a trap. It lets a team propose the best solution for what you can spend, instead of pricing something you cannot afford.
How to read an estimate
When a proposal arrives, look past the total.
Is the scope clear?
Does it list what is included, and what is not? Vague descriptions hide risk. Look for features, platforms, integrations, design, testing and deployment.
Are the assumptions stated?
Good estimates say what they assume: "Assumes one payment provider", "Assumes content is supplied by you", "Assumes existing API is documented". Assumptions show where the price might change.
Is it a range, and is the reasoning shown?
A range with explanation is more trustworthy than a single number with none.
What is included beyond development?
Check for testing, project management, deployment, documentation, training and a support period. These are often missing from the cheapest quotes.
How are changes handled?
There should be a clear process for estimating and approving changes.
What are the payment terms?
Payments tied to delivered milestones protect you better than large upfront sums.
Who is doing the work?
Seniority and team size affect both cost and quality.
Why the cheapest quote is rarely the cheapest project
A very low estimate usually means one of four things.
- A narrower scope than the others, with things you assumed were included left out.
- Less experienced people, who cost less per hour and often take longer.
- Less quality work, fewer tests, thinner documentation, more bugs.
- An expectation of change requests, with a low opening price and increases later.
Compare what is actually included before comparing the total. If one quote is half the others, ask why, in writing.
Methods for controlling the budget
You cannot remove uncertainty, but you can manage it.
Start with discovery
A short paid discovery phase, producing a clear scope, wireframes or a technical plan, reduces uncertainty before the main build. It also lets you test the working relationship.
Build in stages
Split the project into stages with their own estimates and deliverables. You commit to one stage at a time and adjust based on what you learn.
Prioritise ruthlessly
Keep a clear "must have" list for the first release, and a "later" list for the rest. Reducing scope is the most effective way to reduce cost.
Choose a pricing model that fits
- Fixed scope when requirements are clear.
- Staged milestones when they will evolve.
- Dedicated team for long-running work; see hire a dedicated software team.
Hold regular reviews
A demo at the end of each cycle shows progress and catches misunderstandings while they are cheap to fix.
Track scope changes openly
Agree that any addition has a visible cost and trade-off. Adding something means removing something, or increasing the budget. Visibility prevents "scope creep" from being a surprise.
Common estimation mistakes
- Treating an early estimate as a promise. Early figures are ranges.
- Comparing totals without comparing scope.
- Forgetting non-development work, such as testing, design, communication and deployment.
- No contingency. Something always turns up.
- Ignoring maintenance. The build is not the whole cost; see software maintenance costs.
- Letting requirements drift without review.
- Pressuring the team for a lower number. The work does not shrink; quality does.
- Not involving the people who will do the work. Estimates made by salespeople alone are often wrong.
- Deciding alone. Involve users and stakeholders early so requirements are right.
Questions to ask about any estimate
- What exactly is included and excluded?
- What assumptions is this based on?
- What are the biggest risks, and how do they affect the price?
- How much contingency is included?
- How will we know if we are going over budget?
- How are changes estimated and approved?
- What happens after launch, and what does it cost?
- Who will do the work, and at what seniority?
- What could we remove to reduce the cost?
A simple planning approach for founders
If you need a number to plan with, this approach works for most projects.
- Write a one-page brief covering goals, users, must-haves and constraints.
- Ask two or three teams for ranges, with their assumptions.
- Compare scope first, then price.
- Pick the team you trust most, not simply the lowest number.
- Start with a discovery or first stage, so your real estimate improves with evidence.
- Budget a buffer of at least 15 to 20 percent above the likely figure.
- Plan the running costs from day one.
Final thoughts
An estimate is a map drawn before the journey. It will not be perfect, but a thoughtful one will get you where you need to go, and show you the turns where the route might change. The teams worth hiring are not the ones who promise an exact number immediately, but the ones who ask good questions, explain their assumptions and help you shape the scope to fit your budget.
If you would like an estimate built that way, describe your project to us. We will ask the questions first, give you a range with its assumptions written down and show you where the choices are that could raise or lower it.