Age-stage cost composition
Scenario comparison
Scenario table
| Scenario | Total projected cost | Avg / month | % of income | Pre-fund / month |
|---|
How this rebuild fixes the old savings glitch
The old version could show a very large monthly savings number because it treated the entire 0–18 cost as something to fully fund over a short savings window. That is not how most families budget for children.
This rebuild uses average monthly child cost as the default planning number. Optional pre-funding still exists, but it is separated so it no longer replaces the real budgeting signal.
Core formulas
Stage yearly cost = stage category totals + annual spikes
Stage projected cost = stage yearly cost × years in stage, grown by annual inflation
Gross projected cost = age 0–3 stage + age 4–12 stage + age 13–18 stage + optional work reduction cost
Support offset = annual support × support years, grown by annual inflation
Net projected cost = gross projected cost − support offset
Safety margin = net projected cost × safety margin %
Total projected cost = net projected cost + safety margin
Average monthly child cost = total projected cost ÷ remaining months
Current stage monthly cost = current stage yearly cost ÷ 12
Optional pre-fund monthly target = (total projected cost − current child fund) ÷ months to pre-fund
Stage projected cost = stage yearly cost × years in stage, grown by annual inflation
Gross projected cost = age 0–3 stage + age 4–12 stage + age 13–18 stage + optional work reduction cost
Support offset = annual support × support years, grown by annual inflation
Net projected cost = gross projected cost − support offset
Safety margin = net projected cost × safety margin %
Total projected cost = net projected cost + safety margin
Average monthly child cost = total projected cost ÷ remaining months
Current stage monthly cost = current stage yearly cost ÷ 12
Optional pre-fund monthly target = (total projected cost − current child fund) ÷ months to pre-fund
Default planning output is the average monthly child cost, not the optional pre-fund amount.
Frequently Asked Questions
Why is average monthly cost the main output now?+
Because most families pay for children through ongoing household cash flow, not by fully pre-funding 18 years in one short savings period.
Why can the pre-fund target still be very high?+
Because it intentionally answers a different question: how much would you need to save now if you wanted to build a large funding pot quickly. It is optional and no longer the default planning number.
Why was age 4–12 lowered and age 13–18 raised?+
Because the school-age period often dips when primary school is mostly free, while teen years often rise because of food, clothing, technology, transport and social costs.
What is the work reduction cost input for?+
It captures the household income loss when one parent drops working hours, which is one of the most important hidden family costs in practice.
Does this include higher education?+
No. This version ends at age 18. Higher education support should be treated as a separate planning layer.