MVP Calculator Walkthrough: Estimating Your Project
Learn how to use NextBuild's MVP calculator to estimate your project timeline and budget. Step-by-step walkthrough with real examples and common pitfalls to avoid.
October 6, 2024 10 min read
Every founder asks the same question: "How much will this cost and how long will it take?" The frustrating answer from most agencies is "it depends." That's technically true, but it's not helpful.
We built our MVP calculator to give you a real answer in five minutes. Not a vague range, but a concrete estimate based on the features you actually need. After using this calculator with hundreds of founders, we've learned that the estimation process itself often clarifies what you're building more than any discovery call.
This walkthrough covers exactly how to use the calculator, what each input means, and how to interpret the output. More importantly, it explains the logic behind the numbers so you can evaluate any development estimate—not just ours.
Why Accurate Estimation Matters More Than You Think
Bad estimates kill startups. Not immediately, but slowly. A project that takes twice as long as expected burns through runway you planned to use for marketing. A budget that doubles mid-project forces hard choices about features that seemed essential.
The reverse problem is equally dangerous. Underbuilding because you underestimated costs leaves you with a product that can't compete. Cutting corners on infrastructure because "we'll fix it later" creates technical debt that compounds.
Good estimation isn't about predicting the future perfectly. It's about making decisions with realistic information. When you know a feature adds three weeks and $8,000, you can make an informed choice about whether it's worth it for launch.
Before touching the calculator, understand the three factors that drive every software estimate:
: What are you actually building? This includes features, screens, integrations, and user types. Scope is where most estimation goes wrong—not because engineers can't estimate, but because founders haven't defined what they want.
Stop planning and start building. We turn your idea into a production-ready product in 6-8 weeks.
Scope
Complexity: How hard is each piece to build? A user login is straightforward. Multi-tenant authentication with SSO and custom permissions is not. Same category, wildly different effort.
Risk: What might go wrong? Third-party integrations fail. APIs change. Edge cases appear. Good estimates account for unknowns.
The calculator addresses all three, but it can only work with the inputs you provide. Garbage in, garbage out.
Starting the Calculator: Your Product Category
The first question asks what type of product you're building. This isn't arbitrary categorization—it determines the baseline assumptions.
Marketplace: Two-sided platforms connecting buyers and sellers. These have inherent complexity around transactions, trust, and communication between parties.
SaaS Application: Single-purpose software solving a specific problem. Usually simpler than marketplaces because you control both sides of the interaction.
Consumer App: Products for general consumers rather than businesses. Often prioritize UX polish and require broader device support.
B2B Tool: Business-facing applications. Usually fewer users but higher expectations for reliability and specific workflow support.
Fintech: Any product touching money. Adds compliance requirements, security considerations, and often third-party integrations.
Healthtech: Products dealing with health data. HIPAA compliance isn't optional, which affects architecture choices.
Each category comes with baseline assumptions about authentication, data handling, and typical integrations. A fintech product assumes you'll need payment processing. A consumer app assumes you'll need social login. These assumptions speed up estimation without asking twenty additional questions.
Feature Selection: The Heart of the Estimate
The feature section is where most of the estimate is determined. Each feature has been priced based on actual development time across dozens of projects.
Core Features
User Authentication: Basic email/password plus social login. We use Clerk for most projects, which handles the complexity behind a clean API. This is table stakes—nearly every MVP needs it.
User Profiles: Editable profiles with settings. More complex than it sounds because it touches permissions, file uploads (avatars), and validation.
Admin Dashboard: Backend interface for managing users, content, or settings. Complexity scales with what you need to manage.
Notifications: Email and push notifications. Includes the infrastructure for templates, delivery tracking, and user preferences.
Search: Finding content within your application. Can range from simple filtering to full-text search depending on your data.
Business Logic Features
Payments: Stripe integration for one-time or recurring payments. Includes subscription management, invoicing, and webhook handling.
Booking/Scheduling: Calendar-based reservation systems. Deceptively complex because of timezones, conflicts, and cancellation policies.
File Uploads: User-generated content like images or documents. Includes storage, processing, and delivery optimization.
Messaging: In-app communication between users. Real-time adds complexity but is often expected.
Reviews/Ratings: User feedback systems. Includes moderation considerations.
Each feature you select adds to the estimate. The calculator shows the impact in real-time so you can see tradeoffs immediately.
Platform Selection: Where Will This Run?
Platform choice affects both initial development and long-term maintenance.
Web Only: A responsive website that works on desktop and mobile browsers. Fastest to build, widest reach, easiest to update.
Web + iOS: Adds a native iPhone app. Near-doubles development time because you're building two interfaces with different constraints.
Web + iOS + Android: Full coverage across all major platforms. Typically adds 40-50% over web + iOS because Android and iOS share significant logic.
Mobile Only: No web presence. Uncommon for MVPs because it limits your market and makes iteration slower.
Our recommendation for most startups: launch with web only. Mobile apps are harder to update, require app store approval, and have higher user acquisition costs. Prove the concept on web, then add mobile when you have clear mobile-specific demand.
Timeline Preferences: Speed vs. Cost
The calculator offers three timeline options:
Standard (8-12 weeks): Optimal balance of speed and cost. Room for iteration and proper testing. This is where most MVPs land.
Accelerated (6-8 weeks): Faster delivery, higher cost. Requires more parallel work and tighter coordination. Makes sense when time-to-market is critical.
Extended (12-16 weeks): More buffer for complex integrations or compliance requirements. Lower weekly cost because work is spread out.
Faster timelines don't just cost more per week—they also introduce risk. Compressed schedules leave less room for discovery and problem-solving. If something goes wrong in an accelerated project, you don't have slack to absorb it.
Understanding the Output
After completing the inputs, the calculator produces three numbers:
Estimated Timeline: The projected duration from kickoff to launch. This assumes reasonable client responsiveness—delays on your side extend the timeline.
Investment Range: A low-to-high cost estimate. The range accounts for complexity variations within your selected features. A simple booking system is at the low end; a complex multi-resource calendar is at the high end.
Monthly Maintenance: Estimated ongoing costs after launch. Includes hosting, monitoring, minor updates, and bug fixes. This number matters for runway planning.
The range isn't padding. It reflects genuine uncertainty about implementation details. When you discuss specifics in a discovery call, the range narrows.
Common Mistakes in Self-Estimation
After watching hundreds of founders use the calculator, patterns emerge in how estimates go wrong.
Underestimating Admin Functionality
Founders think about user-facing features but forget the back-office tools. Your marketplace needs a way to handle disputes. Your SaaS needs usage dashboards. Your booking app needs cancellation management.
Admin features often equal or exceed user-facing features in complexity. The calculator includes basic admin in most feature selections, but custom admin requirements push estimates higher.
Assuming Integrations Are Simple
"We just need to connect to their API" is rarely just anything. Third-party integrations involve:
Authentication: OAuth flows, API key management, token refresh
Data mapping: Their format to your format
Error handling: What happens when the API is down
Rate limiting: Respecting usage limits without degrading your product
Versioning: APIs change, and you need to change with them
A "simple" integration typically adds one to two weeks. Complex integrations with poor documentation can take longer than building the feature they support.
Forgetting Mobile Complexity
Mobile apps aren't just responsive websites wrapped in native chrome. They involve:
Device fragmentation: Testing across screen sizes and OS versions
Update distribution: Rollout strategies and version management
If you selected mobile platforms, the estimate accounts for this. If you're surprised by the mobile premium, that's the reality of multi-platform development.
Scope Creep Through Feature Combinations
Individual features interact in ways that add complexity. User profiles plus messaging means profiles need privacy controls. Payments plus subscriptions means handling plan changes mid-cycle. Search plus real-time means search results need to update live.
The calculator accounts for common interactions, but unusual combinations may require discussion. If your feature set seems to create unique requirements, note them for the discovery call.
Using the Estimate in Planning
A calculator estimate is a starting point, not a contract. Use it for:
Fundraising planning: Know whether you need to raise $50K or $500K before you pitch. Nothing derails investor conversations faster than unrealistic development expectations.
Timeline setting: Align development expectations with market timing. If you need to launch before a competitor or seasonal opportunity, you know whether acceleration is feasible.
Vendor evaluation: Compare agency quotes to the calculator baseline. If someone quotes half the calculator estimate, ask what they're leaving out. If they quote double, ask what additional value they're providing.
From Calculator to Discovery
The calculator produces a useful estimate. A discovery call produces a real one.
During discovery, we dig into specifics that the calculator can't capture:
User journeys: What exactly happens when a user does X? The steps between "user books appointment" and "appointment happens" contain dozens of decisions.
Edge cases: What if the payment fails? What if the user loses internet mid-action? What if two users try to book the same slot?
Integration specifics: Which specific providers do you need to integrate? What does their API documentation actually look like?
Existing assets: Do you have designs? Branding? Previous technical work? Starting points affect the estimate.
Discovery typically refines the calculator estimate by 20-30% in either direction. Sometimes features are simpler than assumed; sometimes requirements hidden in "obvious" functionality emerge.
When the Calculator Doesn't Apply
Some projects fall outside calculator scope:
Highly regulated industries: Beyond standard fintech and healthtech, some products require specialized compliance that needs custom assessment.
Hardware integration: IoT, embedded systems, or products requiring custom hardware have unique requirements.
Legacy system replacement: Migrating from existing software involves discovery that can't be estimated without examining the current system.
Research and development: Novel technology or unproven approaches involve experimentation that doesn't fit traditional estimation.
For these projects, skip the calculator and schedule discovery directly. The conversation will be more productive than hypothetical numbers.
Key Takeaways
The MVP calculator gives you a realistic starting point for project planning. To use it effectively:
Be honest about scope: Include everything you actually need, not just the headline features
Start with web: Add mobile platforms only when you have clear mobile-specific requirements
Account for admin: User-facing features need management interfaces
Respect integration complexity: Third-party connections take real time
Use the range: The low end assumes smooth execution; the high end assumes realistic complications
The goal isn't a perfect estimate—it's an informed starting point for conversation. Armed with realistic numbers, you can make better decisions about features, funding, and timeline.
Ready to get a detailed estimate for your specific project? Use our MVP calculator to get started, then schedule a discovery call to refine the numbers and discuss your requirements.
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