How do I work out my buildings sum insured?

Use the rebuild cost, not the market value or the purchase price. Rebuild cost covers demolition, site clearance, materials, labour, professional fees and meeting current building regulations, and excludes the land. The industry standard is the BCIS rebuild calculator provided through the ABI, which prices by construction type, age and region. For listed, thatched or non-standard properties, commission a reinstatement cost assessment from a chartered surveyor instead.

Why is rebuild cost lower than what my house is worth?

Because the market value includes the land, the location and what someone is willing to pay, none of which need rebuilding after a fire. In much of the UK the land is a large share of the price, so insuring for the purchase price means paying a premium on a sum you could never claim. The reverse applies to listed or unusually constructed homes, where rebuilding can cost more than buying.

What happens if I am underinsured?

Most policies apply an average clause, which reduces every settlement in proportion to the shortfall rather than only capping total losses. If you insure for £150,000 against a £200,000 true rebuild cost, you are covered for 75%, so a £20,000 kitchen fire is settled at around £15,000. That is why underinsurance causes problems on ordinary claims, not just catastrophic ones.

How much contents insurance do I need?

Work it out room by room rather than guessing a total. Contents is everything you would take if you moved: furniture, clothes, electronics, kitchenware, carpets and curtains, bikes, tools, and the contents of the loft, garage and shed. Total what each room would cost to replace new. Most people underestimate substantially, because individually the items are unremarkable and collectively they are not.

What is a single-article limit?

The maximum a contents policy will pay for any one item unless it is specified separately, commonly £1,000 to £2,500. A £6,000 engagement ring on a policy with a £1,500 limit is covered for £1,500 no matter how large the overall sum insured is. Valuables usually also carry an overall sub-limit as a percentage of the contents sum, so check both and specify anything above the threshold individually.

Are buildings and contents the same policy?

They are two separate covers, frequently sold together. Buildings covers the structure and permanent fixtures, including fitted kitchens and bathrooms; contents covers what you would take with you. Owners generally need both; tenants usually need contents only, since the landlord insures the building. Claims are settled against whichever cover applies, not against a combined total.

What is the difference between new for old and indemnity cover?

New for old replaces damaged or stolen items with equivalent new ones, with no deduction for age. Indemnity deducts wear and tear, so a five-year-old sofa is settled at its depreciated value rather than replacement cost. Most modern policies are new for old, but not all, and clothing and linen are sometimes excluded from it even where the rest of the contents is covered that way.

Does my contents insurance cover things outside the home?

Not by default. Standard contents cover generally stops at the front door, so bikes, phones, laptops and jewellery taken out of the house need personal possessions cover as an extension. The same applies to a student child's belongings in halls, which many policies will include on request. Check before assuming, because these are among the most commonly claimed-for and most commonly uncovered items.

Home Insurance Sum Insured Calculator

Work out how much buildings and contents cover to ask for, a recommended rebuild sum for your buildings and a recommended contents sum, based on your home's size, type and bedrooms. This is a cover guide, not a premium quote.

A cover guide, not a premium. This calculator gives a simplified guide to how much buildings and contents cover to consider, it is NOT a premium quote and NOT a professional valuation. Buildings sum insured should reflect rebuild cost, not market value. Get a proper rebuild-cost assessment and compare insurer quotes before buying cover.

Enter your home's details

A recommended buildings rebuild sum and contents sum appear here as you type.

How this sum-insured guide is calculated

Buildings insurance should cover the cost to demolish and rebuild your home from scratch, including materials and labour, not what it would sell for on the open market; in many areas these two figures are very different because land makes up a large share of a home's sale price. This calculator estimates a rebuild sum by multiplying your internal floor area by a rebuild rate per square metre (defaulting to a broadly representative £2,000/m², which you can override with a more accurate regional or RICS/BCIS figure) and a house-type adjustment, detached homes have proportionally more external wall per square metre of floor space, so they cost more per m² to rebuild, while flats share structure with neighbouring units and sit at the other end of the scale. Contents insurance is estimated using a simple £15,000-per-bedroom baseline, a rule of thumb used by several UK insurers' own online tools, plus any high-value items add-on you enter for valuables like jewellery or electronics that push you above the baseline or a typical single-article limit. Getting the sum insured right matters: under-insuring buildings can trigger an "average" clause that cuts a claim payout proportionally, and under-insuring contents means a big loss might not be fully covered, so treat these figures as a starting point and get a proper valuation if you're unsure.

Rebuild cost is not market value

This is the mistake that matters most, and it is almost universal. Buildings insurance covers the cost of rebuilding your home from the ground up: demolition, clearing the site, materials, labour, scaffolding, architects' and surveyors' fees, and meeting current building regulations. It does not cover the land, and land is frequently the larger part of what you paid.

The practical consequence is that rebuild cost is usually well below market value, and insuring for the purchase price means paying a premium on a sum you can never claim. In parts of the South East the gap can be enormous.

It runs the other way too. Listed buildings, properties with stone or thatch, anything with non-standard construction, and homes in places that are awkward to get a lorry to can cost far more to rebuild than to buy. Those are exactly the properties where an off-the-shelf estimate is least reliable and a proper assessment is most worth paying for.

The industry reference is the BCIS rebuild calculator provided through the ABI, which prices by construction type, age and region. This calculator uses an adjustable rate per square metre so you can drop in a BCIS or surveyor's figure instead of the default.

Underinsurance and the average clause

If your sum insured is too low, insurers do not simply cap the payout at the sum you chose. Most policies contain an average clause, which reduces the settlement in proportion to the shortfall.

Insure for £150,000 when the true rebuild cost is £200,000 and you are covered for 75% of the value. A £20,000 kitchen fire is then settled at around £15,000, even though it is nowhere near your sum insured. The penalty applies to every claim, not only total losses, which is why underinsurance bites far more often than a house burning down.

Industry surveys have repeatedly found a large share of UK homes underinsured, usually not through carelessness but because a figure set years ago was rolled forward at renewal while building costs rose. Materials and labour have moved sharply in recent years.

Many policies index-link the sum insured automatically, which helps but does not catch an extension, a loft conversion or a new kitchen. Any work that changes the property should trigger a recalculation.

Valuing contents honestly

Contents means everything you would take with you if you moved: furniture, clothes, electronics, kitchenware, carpets and curtains, bikes, tools, the contents of the loft and the shed. It is routinely underestimated, because most of it is unremarkable individually and enormous in aggregate.

The reliable method is room by room rather than a guess for the whole house. Walk each room and total what it would cost to replace the contents new, including the things nobody thinks of: the airing cupboard, the garage, the garden furniture. Photographs of each room are worth taking now, because reconstructing a list after a fire or burglary is extremely difficult.

This calculator starts from a per-bedroom baseline as a sanity check, not as a substitute for that walk-through. Use it to see whether your own figure is in the right region.

Check the cover basis too. New for old replaces items with equivalent new ones; indemnity deducts wear and tear and pays considerably less. Most modern policies are new for old, but not all, and the difference on a houseful of five-year-old furniture is substantial.

Single-item limits and high-value possessions

Every contents policy has a single-article limit, commonly somewhere between £1,000 and £2,500. Anything worth more than that must be specified individually or it is only covered to the limit, regardless of how large your overall sum insured is.

The usual casualties are engagement and wedding rings, watches, laptops, cameras, bicycles and musical instruments. A £6,000 ring on a policy with a £1,500 single-article limit is insured for £1,500, and the owner generally discovers this at the point of claim.

Valuables also frequently carry an overall sub-limit, often a set percentage of the contents sum, so the total of jewellery, watches and similar is capped separately from everything else. Check both limits, not just one.

Items you take out of the house, bikes, phones, laptops, jewellery being worn, need personal possessions cover, which is a separate extension. Standard contents cover stops at the front door. So does cover for a student child's belongings in halls, though many policies include it as an option worth asking about.

Getting the sum insured right, and keeping it right

For buildings, use a BCIS-based rebuild figure where you can, and commission a proper reinstatement cost assessment from a chartered surveyor for anything listed, unusual or high value. It is a few hundred pounds against a six-figure exposure.

For contents, do the room-by-room walk-through and redo it after any significant purchase. Keep receipts and photographs somewhere that would survive the loss of the house, which in practice means cloud storage rather than a drawer.

Then check the figure at every renewal rather than accepting the rolled-forward number. Index-linking tracks general building cost inflation; it does not know about your extension.

Finally, note that some insurers now offer unlimited or bedroom-rated buildings cover, which removes the sum-insured problem entirely by not asking for one. If your property is hard to value, that is worth seeking out.

Worked example: a 110 m² three-bedroom semi

At the default £2,000 per square metre rebuild rate, with £5,000 of high-value items specified on top of the contents baseline. These are the exact figures this calculator returns.

Internal floor area	110 m²
Property type	Semi-detached
Rebuild rate used	£2,000.00 per m²
Buildings sum insured	£220,000.00
Bedrooms	3
Contents baseline	£45,000.00
High-value items	£5,000.00
Contents sum insured	£50,000.00
Combined total (two separate covers)	£270,000.00

The £220,000 buildings figure is what it would cost to rebuild, and it is entirely unrelated to what the house would sell for. The two sums are also separate covers rather than one policy limit: the £270,000 total is shown for reference only, and a claim is settled against whichever of the two it falls under.

Frequently asked questions

How do I work out my buildings sum insured?: Use the rebuild cost, not the market value or the purchase price. Rebuild cost covers demolition, site clearance, materials, labour, professional fees and meeting current building regulations, and excludes the land. The industry standard is the BCIS rebuild calculator provided through the ABI, which prices by construction type, age and region. For listed, thatched or non-standard properties, commission a reinstatement cost assessment from a chartered surveyor instead.
Why is rebuild cost lower than what my house is worth?: Because the market value includes the land, the location and what someone is willing to pay, none of which need rebuilding after a fire. In much of the UK the land is a large share of the price, so insuring for the purchase price means paying a premium on a sum you could never claim. The reverse applies to listed or unusually constructed homes, where rebuilding can cost more than buying.
What happens if I am underinsured?: Most policies apply an average clause, which reduces every settlement in proportion to the shortfall rather than only capping total losses. If you insure for £150,000 against a £200,000 true rebuild cost, you are covered for 75%, so a £20,000 kitchen fire is settled at around £15,000. That is why underinsurance causes problems on ordinary claims, not just catastrophic ones.
How much contents insurance do I need?: Work it out room by room rather than guessing a total. Contents is everything you would take if you moved: furniture, clothes, electronics, kitchenware, carpets and curtains, bikes, tools, and the contents of the loft, garage and shed. Total what each room would cost to replace new. Most people underestimate substantially, because individually the items are unremarkable and collectively they are not.
What is a single-article limit?: The maximum a contents policy will pay for any one item unless it is specified separately, commonly £1,000 to £2,500. A £6,000 engagement ring on a policy with a £1,500 limit is covered for £1,500 no matter how large the overall sum insured is. Valuables usually also carry an overall sub-limit as a percentage of the contents sum, so check both and specify anything above the threshold individually.
Are buildings and contents the same policy?: They are two separate covers, frequently sold together. Buildings covers the structure and permanent fixtures, including fitted kitchens and bathrooms; contents covers what you would take with you. Owners generally need both; tenants usually need contents only, since the landlord insures the building. Claims are settled against whichever cover applies, not against a combined total.
What is the difference between new for old and indemnity cover?: New for old replaces damaged or stolen items with equivalent new ones, with no deduction for age. Indemnity deducts wear and tear, so a five-year-old sofa is settled at its depreciated value rather than replacement cost. Most modern policies are new for old, but not all, and clothing and linen are sometimes excluded from it even where the rest of the contents is covered that way.
Does my contents insurance cover things outside the home?: Not by default. Standard contents cover generally stops at the front door, so bikes, phones, laptops and jewellery taken out of the house need personal possessions cover as an extension. The same applies to a student child's belongings in halls, which many policies will include on request. Check before assuming, because these are among the most commonly claimed-for and most commonly uncovered items.

Also known as: contents insurance calculator · home insurance calculator · buildings insurance calculator · how to work out buildings sum insured · rebuild cost calculator · building and contents insurance calculator · how much buildings insurance do I need · property sum insured calculator