Wedding vs House Deposit: The Opportunity Cost

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摘要

The average UK wedding costs £20,000–£26,000 (Bridebook 2025). For a couple also saving for their first home, that’s a significant portion of a typical house deposit. This calculator answers a simple question: how many extra months will your wedding add to your deposit timeline?

It works by computing two savings timelines — one where you save purely for a deposit, and another where you also need to cover the wedding cost — then showing the difference and the long-term opportunity cost of that money.

工作原理

The calculator models two parallel savings paths:

Without wedding: Save monthly at a given interest rate until you reach the deposit target.
With wedding: Save monthly until you reach the deposit target plus the total wedding cost (the assumption is you pay for the wedding from the same savings pot before buying).

The difference in months between the two paths is the “delay” your wedding adds to homeownership.

It also computes the opportunity cost — what the wedding money would be worth if invested over 5, 10, and 25 years at the same rate.

The formulas

months_to_target = number of months until balance ≥ target

Where

balance= Running total, updated each month: balance = balance × (1 + r/12) + monthly_savings

r= Annual savings interest rate (decimal)

monthly_savings= Amount saved per month (£)

target= Deposit amount, or deposit + wedding cost

opportunity_cost = wedding_cost × (1 + r)^years

Where

wedding_cost= Total wedding expenditure (£)

r= Annual return rate (decimal)

years= Investment horizon (5, 10, or 25 years)

The savings accumulation is computed iteratively (month-by-month) rather than with a closed-form formula, because the iterative approach naturally handles the discrete compounding and avoids fractional-month rounding issues.

UK wedding cost benchmarks (2025)

Wedding style	Typical guests	Typical total cost
Intimate / Budget	30	£7,000–£10,000
Traditional British	80–120	£20,000–£26,000
South Asian	200–400	£40,000–£100,000
Luxury / Country House	100–200	£50,000–£80,000

Sources: Bridebook 2025 UK Wedding Report (6,800 couples), Hitched 2024 Survey (3,000 couples), Mii Asian Catering.

计算示例

Traditional wedding (100 guests) vs £300k house, 10% deposit

Calculate total wedding cost

Venue £5,000 + Catering £75×100 + Drinks £30×100 + Photography £1,800 + Flowers £1,000 + Attire £2,000 + Music £800 + Cake £400 + Invitations £200 + Transport £500 + Honeymoon £3,500

= £25,700

Calculate deposit target

£300,000 × 10%

= £30,000

Months to save deposit only (£800/mo, 4% interest)

Month-by-month accumulation until balance ≥ £30,000

= 36 months (3 years)

Months to save deposit + wedding (£800/mo, 4% interest)

Month-by-month accumulation until balance ≥ £55,700

= 63 months (5 years 3 months)

Extra delay

63 − 36

= 27 months (2 years 3 months)

Opportunity cost at 25 years

£25,700 × (1.04)^25

= £68,512

Result

A traditional British wedding delays your deposit by 27 months and has a 25-year opportunity cost of £68,512

输入说明

Wedding style — preset cost templates (Budget, Traditional, South Asian, Luxury) with typical guest counts and itemised costs. Users can customise every item.
Number of guests — scales per-head costs (catering, drinks).
Itemised wedding costs — 11 categories (venue, catering, drinks, photography, flowers, attire, music, cake, invitations, transport, honeymoon). Fixed items have a flat cost; per-head items multiply by guest count.
Property price — target property value.
Deposit % — typically 5–25%. Higher deposits unlock better mortgage rates.
Monthly savings — how much the household saves per month.
Savings interest rate — annual rate on savings account (easy access ISAs typically 4–4.5% in early 2026).

输出说明

Extra months — the headline: how many additional months the wedding adds to the deposit timeline.
Total wedding cost — sum of all itemised costs.
Target deposit — property price × deposit percentage.
Deposit timeline (no wedding) — months to save the deposit.
Deposit timeline (with wedding) — months to save deposit + wedding cost.
Opportunity cost (5/10/25 years) — what the wedding money would grow to if invested instead.
Cost breakdown — horizontal bar chart showing each wedding item’s contribution, sorted by spend.
Timeline comparison — visual bar comparing the two savings paths.

假设与局限

Sequential saving model: Assumes you save for both the wedding and the deposit from the same pot, paying for the wedding first. In practice, some costs may be spread over time or paid by family contributions.
No family contributions: Many UK weddings receive financial help from family. The calculator shows the full cost to the couple.
Same rate for savings and investment: The opportunity cost uses the savings rate, not a stock market return. This is conservative — actual investment returns would likely make the opportunity cost higher.
No inflation adjustment: Wedding costs and property prices are in today’s money. Over multi-year timelines, both may increase.
Monthly compounding: Interest is applied monthly, matching how most UK savings accounts work.
No Help to Buy / Lifetime ISA: Government schemes that boost deposit savings are not modelled.

验证

Test case	Wedding cost	Deposit target	Extra months	OC 25yr	Verified by
Traditional, 100 guests, £300k, 10%, £800/mo, 4%	£25,700	£30,000	27	£68,512	Manual month-by-month calc
Budget, 30 guests, £200k, 5%, £500/mo, 3%	£7,600	£10,000	14	£15,913	Manual month-by-month calc
Luxury, 150 guests, £500k, 15%, £1,500/mo, 5%	£67,300	£75,000	35	£227,902	Manual month-by-month calc