Turn three estimates into one expected value
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PERT gives the most-likely estimate extra weight while preserving uncertainty at both ends.
See how your MVP estimate is built
WebGrid turns a prioritized scope into optimistic, expected, and cautious ranges for effort, cost, and delivery time.
Every input is visible and editable. The same scope and assumptions always produce the same result—without AI inference.
- Start with the features needed for the first useful release.
- Adjust for delivery conditions your team already understands.
- Use the range to compare options, not as a fixed quote.
At a glance
Three decisions shape the result
Keep the first pass simple. You can refine assumptions after the range is useful.
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Prioritize scope
Choose what belongs in the first useful release.
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Adjust delivery
Reflect platforms, complexity, coverage, and team capacity.
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Compare the range
Read optimistic, expected, and cautious outcomes together.
1. Establish base effort
Estimate the release you intend to build
Each catalog feature stores optimistic, most-likely, and pessimistic implementation effort in person-days.
Only first-release priorities count
Included in MVP
Must have
Should have
Post-MVP scope
Could have
Later
Move a feature between priorities to see its impact immediately.
2. Adjust for delivery
Make real project conditions visible
The calculator changes effort only when a selected condition changes the work.
Delivery shape
Platforms, roles, integrations, scale, language, tenancy, and selected risks adjust the range.
Whole-team coverage
Product, design, QA, security, accessibility, and release work remain visible instead of being hidden inside coding.
Contingency
The selected contingency is applied to the optimistic, PERT expected, and cautious effort bands.
See conditions that can change effort
Examples include additional platforms, more user-role boundaries, multilingual delivery, multi-tenancy, higher launch scale, payments, realtime behavior, data migration, complex integrations, compliance, offline support, and custom design.
Multipliers combine when conditions interact. Removing a selected condition removes its multiplier.
3. Convert effort into a plan
Read cost and timeline as ranges
Editable commercial and capacity assumptions convert person-days into planning outcomes.
Adjusted person-days × blended daily rate
An hourly rate is converted using eight hours per day. Rates and currency stay editable; displayed totals are rounded so they do not imply invoice-level precision.
Adjusted person-days ÷ productive team person-days per week
Timeline uses adjusted person-days ÷ productive team person-days per week, then adds discovery and release buffers. Capacity should allow for coordination and support; larger teams do not scale linearly.
How empty and uncalculable estimates are shown
0 is reserved for no customer-confirmed work. Suggested calculator defaults do not count as confirmed until the customer changes or confirms a step. In that state, rates, multipliers, and fixed delivery weeks are not charged. If work is confirmed but its effort benchmark or a required numeric assumption is missing or invalid (for example, zero productive capacity), the affected estimate is shown as ∞ instead of silently substituting a finite fallback. A zero day rate remains a valid way to model a zero budget.
4. Read estimate confidence
See how much of the range is evidence-backed
An untouched estimate is Not started. After the first input is changed or confirmed, it moves through Early, Directional, Planning, and Refined phases as product, launch, scope, complexity, and delivery details are reviewed.
A bounded confidence index, not a delivery probability
The untouched state has an index of 0. Once work is confirmed, the index rises from 20 to 90 as relevant input is reviewed. It stays below certainty because a benchmark estimate is still a planning model, and it does not claim a statistical chance of finishing on time or on budget.
Missing evidence widens the outside edges
While details are missing, the optimistic and cautious edges widen by up to 35% of expected effort. The PERT expected point stays unchanged, and the extra widening falls to zero as every tracked input is reviewed.
Boundaries
Know what the range covers
Selected product-delivery work is included. External costs and commitments are not added silently.
Included when selected
- Feature implementation and integration effort.
- Product, design, QA, security, accessibility, and release coverage.
- Explicit scope multipliers and contingency.
- Discovery and production-release timeline buffers.
Not automatically included
- Taxes, payment fees, hosting, licenses, devices, and app-store fees.
- Marketing, sales, legal advice, certification, support, or content production.
- Unknown legacy-system remediation beyond the selected risk allowance.
- A fixed-price quotation or guaranteed delivery date.
Use the model
Start broad. Refine only what changes the decision.
Compare scope options, document uncertainty, and replace assumptions with evidence during discovery.