How did you calculate if you could afford another child

[SodOffCovid]

Don't mean to be dim here but I feel like I'm losing my mind trying to work out childcare costs going forward and IF we were to decide to have a third. My youngest is only five months old so I'm getting ahead of myself but the discussion has started because we are weighing up saving to move home on the next few years or not. We're currently in a three bed and DH is adamant we would need four beds if we have a third.

Thing is, we pay for a childminder atm for our two year old. He will be eligible for 30 free hours in January and off to nursery school next September. I just can't fathom our how childcare costs will look when he needs wrap around care and the summer holidays. Presumably my child minder could take him for the three days I work in the summer hols, but then they charge half rate of they or I go on holiday.... Its so confusing.

Is there a logical way for me to work out if I can afford a third in the coming years (I appreciate my job may change etc so there are uncertainties)

I should add we are on the voucher scheme so I purchase these to spread the cost over the year as costs fluctuate

I never thought about it financially. I only considered if I could be bothered with the hard work and the damage to my body (the answer was no).

As childcare for a baby tends to be the most expensive, we worked out how much childcare for the baby would be and then multiplied it up by the number of children. That gave us an actual current maximum and allowed for prices to rise over time, and a bit of extra leeway for extra childcare hours if we needed them.
I'm very risk averse though - so I wanted to make sure we had a large buffer.

If you're trying to calculate more accurately I'd use a local average for morning/after school wrap around care and assume that they will be in holiday club or similar (again use a local average cost) for 10 weeks of school holiday to allow yourself a buffer.
Work out monthly values based on the cost being spread over the year. Then you don't need to worry about August being more expensive.

For us it was pretty straightforward, we knew we could afford what we were already paying for nursery and we waited until eldest one was out of nursery. That way, we never had to pay twice. Will you need wraparound care or holiday club or can you cover some of it with flexible working or AL? You will be on maternity leave presumably for some of that time.

We don't use wraparound care. We just balance the school runs between us and work flexibly. Holiday club is open 3 days a week and that works out to be about £30 per session. I work compressed hours so I have Fridays off and then dh or I will use AL to cover the other day or he will take dd to work with him (it's his business so that's easy to do). It works out to be about £100 per week. We've off over Christmas and Easter anyway (paid leave as my work is closed). So it's really only half terms we need coverage for and the summer holidays.

You can ask your nursery what their hourly rate is and then work out with 30 funded hours how many, if any, you'll need to pay for in addition to those. Then take 20% off for tax free childcare.

We did a bit of a spreadsheet. We put bills and things like that in for a couple of months so we could check what we spent on essentials in an average month (we're a bit erratic with food spending, changes a lot from month to month as we like to do a bit of entertaining sometimes).

Basically we looked at what we each took home each month, took off essential spending (including estimate of childcare for DD, who we had planned to increase to 4 days next academic year), and looked at what was left. In our case, it wasn't quite enough to cover what we'd estimate spending on nursery fees after my mat leave would finish (we'd put a bit aside separately for the mat leave itself). We don't have much of a mortgage at the moment, so we decided to reduce our monthly payments on a fixed term of 3 years (we had just finished one contract so could do this), with the hope that when the next DC was getting the free hours we could start overpaying/have another look at our finances as DH is early in his career and will hopefully have moved up a couple of points by then.

However, we then found that I'm expecting twins, which totally messed up the calculation! So our careful planning hasn't quite worked out... my very lovely mum is hoping to be able to pitch in on some days (let's assume Corona is no longer an issue by then) to help reduce costs. Alternatively I'll go full time earlier than planned.