Estimate for Mobile Projects — What It Is, Task Estimation Methods

What Is an Estimate?

Estimate (from English — assessment) is a prediction of the amount of time or effort required to complete a task. In mobile development, estimates can be expressed in hours, days, story points, or monetary terms. The purpose of an estimate is not an exact prediction but reducing uncertainty for decision-making.

How an Estimate Differs from a Commitment

Estimate is a forecast with margin of error. Commitment is a promise to complete a task by a certain date. The difference is critical: an estimate says “probably 5 days,” a commitment says “we’ll do it in 5 days.” Managers often confuse these concepts, turning an estimate into a deadline with no room for error.

Estimate as a Communication Tool

The estimation process is no less important than its result. When a team discusses a task estimate, hidden requirements, dependencies, and risks come to light. Even if the final number is inaccurate, the discussion gives all participants an understanding of the task. That is why collective estimation methods (Planning Poker) are more effective than individual ones.

Estimation Methods in Development

There are several estimation methods, each suited for different project stages and levels of detail. The choice of method depends on available data and required accuracy.

Planning Poker

Planning Poker is the most popular estimation method in Agile. Each developer gets a deck of cards with Fibonacci numbers (1, 2, 3, 5, 8, 13, 21). After discussing the task, everyone reveals their card simultaneously. If estimates diverge, developers with the minimum and maximum estimates explain their reasoning, then a revote follows. This method eliminates authority bias and produces a more accurate estimate.

T-Shirt sizing

T-Shirt sizing is a rough estimate by t-shirt size: XS, S, M, L, XL, XXL. This method is used for quick estimation of large tasks (epics) at early stages when details are unknown. Later, each such task is decomposed and estimated in Planning Poker. T-Shirt sizing takes 5-10 minutes per task but only provides an order of magnitude.

Three-point estimation (PERT)

PERT uses three estimates: optimistic (O), pessimistic (P), and most likely (M). The final estimate is calculated using the formula: (O + 4M + P) / 6. This method accounts for uncertainty and gives a more realistic result than a single estimate. PERT is especially useful for tasks with high risks or new technologies.

Estimate Accuracy: Expectations vs Reality

Estimate accuracy depends on the project stage and the amount of known information. The earlier the estimate is made, the higher the margin of error — this is normal and should be factored into planning.

Cone of Uncertainty

The Cone of Uncertainty is a model that describes how estimation error decreases as a project progresses. At the concept stage, the error margin is 400% (a task could take 1 to 4 months). By the sprint stage, it is 20% (1-1.2 months). Understanding this model helps avoid demanding precise estimates at early stages.

Factors Affecting Accuracy

• Task complexity — is it a new technology or a familiar one? Unknowns increase the error margin by 2-3 times.
• Task size — small tasks (up to 2 days) are estimated more accurately than large ones. Decomposition improves accuracy.
• Team experience — a team that has worked together for 6+ months estimates 30-50% more accurately than a new one.
• Historical data — having velocity metrics and cyclometry data improves forecast accuracy.

Relative vs Absolute Estimation

Relative estimation (in story points) is more accurate than absolute estimation (in hours) because people are better at comparing tasks than estimating time. “This task is twice as complex as that one” is a more reliable judgment than “this task will take 8 hours.” Relative estimates do not depend on a specific developer and maintain accuracy when the assignee changes.

How to Improve Estimation Accuracy: Best Practices

Estimation accuracy can be improved through a systematic approach, collective discussion, and analysis of past mistakes. There are several proven practices.

Decomposition to 1-2 Days

Any task estimated at more than 2 days should be decomposed into subtasks. The principle: if a task cannot be estimated with more than 50% accuracy, it is too large. Break it down into steps, each of which is understandable and estimable. After decomposition, the total estimate often turns out to be 1.5-2 times larger than the initial one.

Historical Data and Metrics

Maintain an estimate history and compare it with actual effort. For example: “tasks estimated at 3 story points take on average 4 days, not 2.” Use team velocity for forecasting: if a team completes 20 story points per sprint, do not plan 30. Analyzing past estimate accuracy is the best training for estimation skills.

Anchoring and Calibration

Anchoring is a psychological effect where the first estimate voiced influences all participants. To avoid anchoring in Planning Poker, everyone reveals their cards simultaneously rather than in turn. Calibration is the regular comparison of estimates with actuals: after 10-20 sprints, a team learns to estimate more accurately through feedback.

Risk-Adjusted Estimation

Every task contains hidden risks: developer illness, API issues, requirement changes. Add a risk-adjusted factor to your estimate: for high-risk tasks, a multiplier of 1.5-2; for low-risk tasks, 1.1-1.2. Transparently show the client which risks have been accounted for and how they affect timelines.

Common Estimation Mistakes

Estimation mistakes recur in most teams, regardless of their maturity. Knowing these mistakes is the first step toward fixing them.

Optimistic Bias

The most common mistake is estimating by the best-case scenario: “if everything goes perfectly, we’ll do it in 3 days.” In reality, nothing goes perfectly: bugs, requirement questions, dependent tasks. Solution: estimate by the most likely scenario, not the optimistic one. Use PERT to account for variability.

Estimation Under Pressure

When a manager says “we need it by Friday,” the developer subconsciously adjusts the estimate to that deadline. Estimation under pressure is always understated and leads to missed deadlines. Solution: estimation should precede the deadline, not the other way around. First, the team estimates, then the parties agree on timelines.

Confusing Complexity and Time

Task complexity (how much to think) and time (how much to do) are different metrics. A task can be simple but time-consuming (building 10 screens) or complex but quick (finding a bug in legacy code). Story points typically estimate complexity, while time is derived from team velocity.

Ignoring Context Switching

A developer does not work 8 hours straight on a single task: meetings, code reviews, helping colleagues, and administrative work consume 30-50% of working time. Context switching must be accounted for in the estimate: in reality, a developer writes code for 3-4 hours per day.