How much should you invest every month: £100, £500 or a fixed percentage of your salary?
The honest answer is that you should invest an amount you can maintain after covering essential spending, expensive debt, short-term goals and an emergency fund. A percentage such as 10% or 20% can be a useful starting point, but it should never override the reality of your own budget.
Two people can earn exactly the same salary and have completely different amounts available to invest. Housing costs, children, debts, transport, lifestyle and job security all matter.
That is why the better question is not:
How much should I invest each month?
It is:
How much can I invest every month without weakening the rest of my finances?
At Your Money Mate, my aim is to make UK personal finance and investing practical. This guide gives you a simple framework for choosing a realistic monthly investment not an impressive number that disappears as soon as life becomes expensive.
Why There Is No Perfect Monthly Investment Amount
An investment calculator can show what £100, £300 or £500 a month might become over 10, 20 or 30 years. It cannot see the rest of your life.
It does not know:
- how secure your income is;
- whether you have children or other people depending on you;
- how much expensive debt you are carrying;
- whether your boiler, car or roof is about to need replacing;
- what short-term goals you are saving towards;
- or how you are likely to react when markets fall.
Calculators are useful for understanding time and compounding, but they are only projections. Returns will not arrive in a neat straight line. Markets can go through long periods of weak or negative performance, fees reduce returns, inflation affects spending power and your income may change.
You can use the free UK investment calculator to explore different scenarios, but start with your real finances before choosing the most exciting result.
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What Should Come Before Investing Every Month?
Before automating a monthly investment, look at the foundations underneath it.
1. Essential monthly spending
Start with your mortgage or rent, bills, food, transport, childcare and other genuine essentials. These need to be covered without relying on a credit card or dipping back into your investments.
The free Your Money Mate Budget Planner can show what comes in, what goes out and what is genuinely left each month.
2. Expensive short-term debt
If you are paying a high rate of interest on credit cards, overdrafts or other short-term borrowing, clearing that debt may be a better priority than increasing your investments.
Investment returns are uncertain. The interest charged on debt is not.
This does not mean every mortgage or low-cost finance agreement must disappear before you invest. It means you should understand the interest rate, repayment commitment and risk before deciding where the next pound should go.
3. An emergency fund
Investments should be given time to recover from market falls. If an unexpected bill forces you to sell during a downturn, your monthly plan was probably too aggressive.
The right emergency fund depends on your circumstances. Someone with a stable salary and low commitments may feel comfortable with less cash than a self-employed person with children and variable income.
The point is not to reach one universal number. It is to hold enough accessible cash that a difficult month does not immediately disturb your long-term investments.
If you are still building those foundations, read Before You Try to Get Rich, Fix These 3 Money Mistakes.
4. Short-term savings goals
Money needed for a holiday, house deposit, car, wedding or home repair in the next few years should not automatically be placed in the stock market.
The market could be down precisely when you need to spend it. Keep short-term savings and long-term investments as separate jobs within your financial plan.
The Three Monthly Investment Numbers
Instead of forcing yourself to choose one rigid figure, give yourself three numbers.
| Monthly number | What it means | Example |
|---|---|---|
| Minimum | The amount you can invest even during a difficult month | £25 or £50 |
| Normal | The affordable amount supported by your usual budget | £100 or £300 |
| Extra | Additional money invested after a bonus, strong business month or other genuine surplus | Variable |
Your minimum amount
This is the amount you believe you can invest without fail even when the month is more expensive than expected.
It might be £25, £50, £100 or £250. The exact number matters less than building a repeatable habit.
If £25 is sustainable and £200 would regularly need to be withdrawn again, £25 is the better starting point.
Your normal amount
Your normal contribution should come from your budget, not from an arbitrary online rule.
Once you know what remains after spending, debt repayments, cash savings and short-term goals, choose an amount that still leaves some breathing room. You do not need to invest every pound left at the end of the month.
Automating this contribution soon after payday can help make the habit consistent. Just make sure the amount is affordable before the automation begins.
Your extra amount
Consistency does not mean investing exactly the same amount every month.
If you are self-employed, work on commission or receive bonuses, a flexible approach may suit you better. You can maintain your minimum or normal contribution and add more when income is stronger.
That is how I approach my own investing. My monthly contributions are not identical. I have a regular target, but I can invest larger lump sums at different points because my income varies.
The important thing is having a system that matches your life.
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How Much of Your Salary Should You Invest?
You will often see guidance suggesting that people save and invest 10% or 20% of their income. The popular 50/30/20 budget also places 20% of take-home pay into a combined savings and investing category.
These percentages can be useful reference points. They are not laws.
Using a fixed percentage of your total salary can be misleading because it ignores your expenses. A person earning £2,500 a month with low housing costs may comfortably invest far more than someone earning the same amount with childcare, debt and a much larger mortgage.
A more useful calculation is:
Take-home income − essential spending − debt plan − short-term savings − emergency-fund contribution = available surplus
You can then decide what proportion of that surplus to invest while leaving a reasonable monthly buffer.
For example, imagine someone receives £2,500 after tax and has £755 remaining after their normal spending and savings commitments. Investing £100 would still leave a £655 buffer. Trying to invest the full £755 could leave them reaching for credit when an irregular expense appears.
The best percentage is the one that is affordable in your real budget and sustainable over time.
Is £100 a Month Enough to Invest?
Yes £100 a month is enough to begin building an investment habit and a long-term portfolio.
It may not feel impressive next to someone investing £1,000 a month, but personal finance is not a competition. Your contribution can grow as your income rises, debts end or other costs fall.
For illustration, if £100 were invested at the end of every month for 20 years and achieved an average annual return of 7%, it could grow to roughly £52,000. You would have contributed £24,000, with the remainder coming from hypothetical investment growth.
That is only an illustration. Real returns will vary, fees and inflation matter, and investment values can fall. However, it demonstrates why time and consistency can make a modest monthly amount meaningful.
If you are starting with a lump sum as well, see how I would start investing again with £1,000.
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Should You Increase Your Monthly Investment?
The easiest increases are often the ones you barely feel.
You may be able to raise your contribution when:
- you receive a pay rise;
- a loan or finance agreement ends;
- childcare or commuting costs fall;
- your emergency fund reaches its target;
- you cancel unused subscriptions;
- or your business income increases.
You do not have to send every extra pound into the market. You could improve your lifestyle, strengthen your cash position and increase your investments at the same time.
Review the amount every three to six months rather than constantly changing it. A monthly contribution should be boring enough to continue through both good and bad markets.
Could You Keep Investing During a 30% Market Fall?
This is the psychological part that calculators miss.
Before setting your contribution, ask yourself:
- Could I maintain this amount during an expensive month?
- Would I continue if my portfolio fell by 30%?
- Can I leave this money untouched for at least five years?
If the answer is no, reducing the amount is not failure. It may make your plan stronger.
Investing money you genuinely do not need makes market volatility easier to handle. You are less likely to panic, sell at the wrong moment or repeatedly stop and restart your plan.
Once the amount is settled, your next decision is what to own. For most beginners, it is worth understanding the difference between individual stocks and ETFs before building a portfolio.
A Simple Monthly Investing Checklist
Before confirming your direct debit or standing order, check that:
- your essential bills are comfortably covered;
- expensive short-term debt is under control;
- you have started building accessible emergency savings;
- money for near-term goals is kept separate;
- the investment can remain untouched for at least five years;
- you understand that returns are not guaranteed;
- and the contribution still works in a more expensive month.
If all seven are true, you probably have a far more realistic number than one produced by copying somebody else’s salary percentage.
New investors can also work through the free How to Start Investing in the UK course and compare accounts using the Stocks and Shares ISA comparison tool.
Final Thoughts: Start With a Number You Can Keep
So, how much should you really invest every month?
Invest enough to make progress, but not so much that your wider finances become fragile.
Your minimum amount builds the habit. Your normal amount moves the plan forward. Your extra amount lets you take advantage of stronger months without creating a commitment you cannot maintain.
£25 invested consistently is better than an unrealistic £500 contribution that is cancelled after two months. £100 is enough to start. A percentage can guide you, but your budget should make the final decision.
Use the free Budget Planner to find your genuine surplus, then test the long-term possibilities with the Investment Calculator.
You can also watch the full video on YouTube for a complete walkthrough of the framework.
This article is for information and education only and does not constitute personal financial advice. Investments can fall as well as rise, and you may get back less than you invest.
